CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 1 Document No. 607-0004 Revision L4 (08/04)
INTRODUCTION
The CH1786 family of modems are a full function,
FCC Part 68 approved 2400bps modem. These
modems provide a fast, easy and flexible way to
integrate a modem into any OEM product while
utilizing the minimum amount of PCB space (1.01 ”x
1.27 ”x 0.52 ”). The CH1786 family only requires two
external interfaces: a ITU-U V.24 serial interface that
can be routed directly to a UART, and a Tip and Ring
interface which goes directly to an RJ-11 jack for the
PSTN line connection. The CH1786 can be
controlled with industry standard AT commands and,
hence, is compatible with available industry
communication software.
All CH1786 modems support asynchronous operation
at 2400bps, 1200bps, and 300bps to both Bell and
ITU-U standards. The resident PSTN line interface,
or Data Access Arrangement (DAA), while being FCC
approved, is also Canadian DOT approvable and can
be approved in other countries that require 1500VAC
RMS isolation requirements per UL 1950 Edition 3.
The CH1786 family of modems operate off a single 5-
volt supply. The low power operation and automatic
standby mode make these modems ideally suited for
portable equipment. In addition, their small physical
size affords maximum flexibility in equipment design.
Figure 1. Functional Block Diagram of CH1786.
The CH1786 comes with FCC Part 68 approval and is
shipped from the factory with an FCC Part 68 label
indicating the registration number and ringer
equivalent. This label should be prominently
displayed on the end product.
FEATURES
• Supports Standards ITU-U V.22bis,V.22,Bell
212,and Bell 103
• FCC Part 68 approved and DOT CSA CS-03 Part I
approvable
• UL 1950 and CSA C22.2 950 Listed
• UL File Number: E104957
• AT Command structure with extensions
• 1500 VAC RMS isolation barrier minimum, 2122V
peak surge protection minimum
• Single 5 volt operation
• Low power operation with automatic reduced power
standby mode
• Automatic adaptive and fixed compromise
equalization
• Size: 1.01 ”x 1.27 ”x 0.52 ”(nominal)
• NVRAM allows storage of custom configurations
and telephone numbers
CH1786 FAMILY
CH1786 NVRAM, Voice/ Inject, Hermetic,
Operating Temperature:
0°C to +70°C
CH1786ET NVRAM, Voice/ Inject, Hermetic,
Operating Temperature:
-40°C to +85°C
CH1786NH Non-Hermetic, Operating
Temperature:
0°C to +70°C
Figure 2. Voice/ Data Port Control
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 2 Document No. 607-0004 Revision L4 (08/04)
DESCRIPTION OF FUNCTIONAL BLOCKS
AND DISCUSSION OF BASIC OPERATIONS
Figure 1 contains a functional block drawing of the
CH1786. The CH1786 is a highly integrated, full-
function modem, comprised of a modulator/
demodulator, controller, NVRAM and an FCC Part 68
approved and UL 1950/CSA C22.2 950 listed PSTN
line interface.
Modulation/Demodulation and Modem Controller.
These functions are provided by a monolithic modem
integrated circuit. This IC has built-in facilities to
accommodate integrated AT command control and
contains the necessary resident interfaces for general
communication and routing to the DAA.
Telephone Line Interface or DAA. The CH1786
family of modems is designed to meet 1500VAC RMS
isolation and provide 2122V peak surge protection.
Consequently, the CH1786 satisfies U.S. FCC Part
68 and DOT CSA CS-03 Part I Canadian
requirements, and will meet other international
approval agency requirements that specify these
levels of isolation.
With the exception of the U.S., most countries
(including Canada) require submission of the final
product or system containing the CH1786 to the
appropriate governing regulatory agency for approval.
Typically this is accomplished by submitting the final
end product to an independent test house or
consultant for evaluation. The test house or
consultant then forwards the test results and
applicable documents to the regulatory agency. Call
Cermetek for a list of suggested consultants.
Non-Volatile RAM (NVRAM). The NVRAM present
on the CH1786 is sufficient to store up to two user
customized modem configurations. The AT&Wn
command will store the active modem configuration in
the selected NVRAM locations by specifying an n of 0
or 1.
The AT&Yn command selects the modem
configurations to be automatically recalled and made
active upon a reset or power up. The ATZn
command immediately recalls and activates a stored
configuration. Refer to Tables 4, 5 and 6 for storable
S-Registers and available commands.
The NVRAM can save up to four telephone numbers
with up to 36 digits or modifiers in each telephone
number. The AT&Zn=s command will store s, the
telephone number dial string. The individual NVRAM
telephone number storage locations are selected by
specifying an n of 0, 1, 2, or 3. The ATDTS=n
command will cause the modem to dial the stored
telephone number in location n. NVRAM is not
available on the CH1786LC or CH1786NH.
SUPPORT FEATURES
AT Command Set. A 40-character command line is
supported. The command line starts with AT and
may contain standard or enhanced commands. The
commands are compatible with EIA Document
TR302.2/88-08006.
Serial Host Interface. The serial interface is a V.24
(EIA-232) compatible interface. Ten Bits total: 1 start
bit, 1 stop bit, and eight data bits which can be either
eight bits with no parity or seven odd or even with
parity. The start bit is LOW going. RXD and TXD
data is non-inverted. See pin description in Table 2.
Speaker Interface. The SPK output reflects the
receiver analog input and provides a signal that can
be used to monitor call progress. The SPK signal can
drive a 300 Ω load directly. Typically, the SPK signal
is input into an audio power amplifier and the
amplifier, in turn, drives the speaker coil. The
speaker is activated with the ATMn command. The
speaker volume is adjusted using the ATLn
command, where n is 0, 1, 2, or 3. Increasing
numbers correspond to higher volume. Figure 6
indicates one method of driving an external 8 Ω
speaker.
Phone Control. Cermetek’s CH1786 contains a pin
called Voice or Data (V/D). The V/D pin toggles high
when the modem goes off hook. This pin can be
used to activate a relay which can switch a telephone
on or off the Tip and Ring incoming PSTN lines. This
feature allows any telephone associated with the
CH1786 to be disconnected when a data call is in
progress, thereby preventing the data from being
disturbed by an inadvertent telephone pick-up. See
Figure 2.
Speed and Parity Selection. Prior to call initiation,
the host controller trains the modem to the host
speed (2400,1200 or 300bps) and parity (odd, even,
mark, space, or none) via a host-initiated training
sequence. This training also sets the speed of the
data for originate calls. The CH1786 will
automatically adjust to the originator’s speed when
answering calls.
The CH1786 matches the host’s parity when it returns
status messages to the host. During a data
connection, however, the modem passes parity
through without interpretation or alteration.
Sleep Mode. To minimize power consumption, the
CH1786 includes a power down feature called Sleep
Mode. When activated, the CH1786 will
automatically enter Sleep Mode after 0 to 254
seconds of inactivity. The inactivity delay is selected
using the ATS24 command. The CH1786 is
delivered from the factory with a 5 second inactivity
delay enabled (i.e., ATS24=5). The CH1786 returns
to normal operation when a ring signal is received or
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 3 Document No. 607-0004 Revision L4 (08/04)
upon an input low signal on the TXD pin.
ATS24=255 disables the Sleep Mode and is the
default if no value is set in register S24.
A SLEEP output signal is available to control power to
external devices. In Figure 6, a FET controlled by the
SLEEP signal turns of the external speaker amplifier
when the CH1786 enters Sleep Mode. In Sleep
Mode, power is reduced to approximately 50% of
normal operating power.
Guard Tone. A guard tone of 550 Hz or 1800 Hz can
be generated at 6 dB or 9 dB below the transmit level,
respectively, by using the &Gn command. Refer to
“Cermetek AT Commands and S-Registers reference
Guide” or the Cermetek web site at
http://www.cermetek.com.
Answer Tone. A ITU-U (2100 Hz) or Bell (2225Hz)
answer tone is generated depending on the selected
configuration. Refer to “Cermetek AT commands and
S-Registers Reference Guide” or the Cermetek web
site at http://www.cermetek.com.
Data Encoding. The data encoding conforms to ITU-
U recommendations V.22bis or V.22, or Bell212A, or
103, depending on the selected configuration. Refer
to “Cermetek AT commands and S-Register
Reference Guide” or the Cermetek web site at
http://www.cermetek.com.
Line Equalization. Transmitter and receiver digital
filters compensate for delay and amplitude distortion
during operation on nominal phone lines. In addition,
automatic adaptive equalization in the receiver
minimizes the effects of inter symbol interference.
Transmission Speed. In normal operation, the
originating modem initiates the call and attempts to
connect to the answering modem at a speed
established by the originating modem’s controller
prior to call initiation. This is referred to as the Initial
Trained Rate. Upon receiving the call, the answering
modem will attempt to connect to the originating
modem at its Initial Trained Rate. If these two rates
are identical, the connection is made. If the speeds
differ, the answering modem must adjust its rate or
terminate the call. Table 1 indicates the connection
rate that will result when the calling modem’s Initial
Trained Rate and the answering modem’s Initial
Trained Rate are different.
NOTE
A 2400-baud connection rate will only result if both
modems are initially set at 2400 baud.
Zero Power Mode (CH1786ET only). If an
application calls for zero power during standby
periods, the power may be switched off using external
circuitry and then reapplied when the CH1786’s RI
pin becomes active. The CH1786ET products can
thus be powered down to zero.
Table 1. Connection Rates.
Answering
Modem Initial
Trained Rate
Connection Rate Resulting
When Calling Modem Initial
Rate Is:
300 1200 2400
300 300 1200 1200
1200 300 1200 1200
2400 300 1200 2400
Figure 3. Zero Power Operation.
Referring to Figure 3, the controller activates the relay
switch, supplying power (+5V) to the CH1786ET. In
this configuration, the ring signal is used to “wake up”
the CH1786ET when the CH1786ET is in the power
down state.
The pins of the CH1786ET will be in an undefined
state when power is switched off. This must be taken
into consideration to assure that no unwanted signals
are presented to the CH1786ET during power down.
Ring Indicator (RI). The RI pin follows the frequency
of the ring signal and toggles low when the CH1786
detects an incoming call. The ring signal is typically
20 to 30 Hz and is on for 2 seconds and off for 4
seconds. Although not TTL compliant, the RI pin can,
nonetheless, be utilized to activate external circuitry
including the external RST pin.
When using the RI pin, it is recommended that a
Schmitt Trigger or the Isolated Envelope Detect
Circuit in Figures 3 or 5 be placed between the RI pin
and the external load.
Power Supply. The CH1786 modem module is a
complex set of sub-systems. During the course of
normal operation the CH1786 decodes analog signals
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 4 Document No. 607-0004 Revision L4 (08/04)
from the telephone line that are in the millivolt range.
Steps must be taken by the user to guarantee that
power supply noise on all supply lines, including
ground, does not exceed 50 mV peak to peak. Any
frequency between 20 kHz and 150 kHz must be less
than 500 micro volts peak. If necessary, use
dedicated power and ground planes. Failure to
provide such operating conditions could cause the
CH1786 to malfunction or to function erratically.
The CH1786 requires a single +5V ±5% supply. It is
recommended that by-pass capacitors be placed on
the power supply as close to the modem’s supply
input as practical. It’s recommended a 10 µF
Tantalum capacitor in parallel with a 0.01 µF ceramic
capacitor be used.
Voice/DTMF Tone Injection Port. The CH1786
provides two pins to allow the user to share the
telephone line interface associated with the modem
for voice and DTMF applications. Figure 4 contains a
schematic indicating one possible configuration for
voice/ tone utilization.
WARNING
The CH1786 has been FCC Part 68 approved as a
data modem only. Utilization of the Voice/DTMF
Tone Port requires further registration. FCC will
require that the system, including the CH1786 and
the handset or DTMF transceiver, adhere to Part 68
rules. Voice/Tone Injection is not active on
CH1786NH.
Typically, voice communication would precede data
communications. For this case, the following
commands should be used to configure the CH1786
(Refer to Figure 4):
Figure 4. Voice/Tone Injection.
Enter: ATS0=<CR> Disables auto-answer
Result: OK
Enter: ATS7=255<CR> Disables data-carrier time
Result: OK out
Enter: ATS10=255<CR> Disables lost-carrier time
Result: OK out
The following command sequences illustrate
implementation of common Voice/Tone Port
applications.
1. To answer a voice call.
(a) Enter: ATH1<CR>
Result: OK
(b) Drive V.INJ. HIGH to activate relay.
(c) Begin voice conversation.
2. To switch to data mode.
(a) Drive V.INJ. LOW
(b) At the originate modem:
Enter: ATX1<CR>
Result: OK
3. To disconnect (hang-up) a voice call or a data
call.
(a) Enter: ATH<CR>
Result: OK
4. To place a call to 1234567 using the CH1786’s
DTMF tone generator.
(a) Enter: ATDT1234567;C0<CR>
Result: OK
(b) Drive V.INJ. HIGH
MODEM CONTROL
The CH1786 modem may be controlled by sending
serial ASCII command sequences. The commands
are sent to the modem serially on the TXD pin. After
execution of a received command, the modem
returns a serial status message that can be read on
pin RXD. This message indicates command
completion status. Refer to Table 3 for a complete
list of status messages.
INITIALIZING THE MODEM
Before commands may be sent to the CH1786, the
CH1786 must be initialized. Initialization is a two step
activity consisting of:
1. Hard Reset. This is accomplished by applying a
hardware reset pulse to pin RST or by switching
the power off and then back on.
2. Initial modem training. The CH1786 must be
trained to the host’s speed (2400, 1200, 300bps)
and parity (odd, even, mark, space or none).
These activities are briefly described below.
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 5 Document No. 607-0004 Revision L4 (08/04)
Reset. Upon applying power to the CH1786, the
CH1786 automatically generates an internal reset
pulse. The user may also reset the modem externally
by applying a high-going reset pulse to the RST pin
for at least 10ms after the +5V power supply has
stabilized. Delay sending commands to CH1786 for
200ms after reset has been initiated to allow the
CH1786 time to properly reconfigure.
Training the Modem. Each modem must be trained
to match its host’s speed and parity so that it is able
to recognize serial asynchronous commands sent to it
by the host’s is UART. The host must retrain the
modem each time a reset pulse is applied on RST or
after a RESET serial command has been issued.
Modem Training Command Sequence. The
CH1786 is trained by sending it the following
sequence:
Enter: AT<CR>
Result: OK
Where: A and T may be either upper or lower case
but must be the same case.
<CR> represents carriage return
The AT sequence is referred to as an attention
sequence. The CH1786 will respond with one of the
following status messages, depending on whether it
is optioned for Terse (abbreviated) or Verbose
(English) status messages.
Result: 0<CR> (Terse)
or
Result: <CR><LF>OK<CR><LF> (Verbose)
Where: <CR> represents carriage return (ASCII 13
or HEX 0D).
<LF> represents line feed (ASCII 10 or
HEX 0A).
After responding with an OK, the CH1786 is in idle
mode and is ready to accept additional commands.
An alternate attention sequence A/ may be sent
which behaves much like the AT sequence except
that it causes the previously entered command
specified with an AT prefix to be executed. When
given, both the AT and A/ must be in upper case
ASCII. No carriage return is needed for the A/
command.
THE COMMAND FORMAT
Typical commands consist of three elements: the
attention sequence, the commands themselves, and
a terminating carriage return.
AT[commands]<CR>.
Where: AT represents attention sequence.
[Commands] represents command strings.
<CR> represents carriage return (ASCII 13
or HEX 0D).
When entering commands to the modem, the
backspace character-control-H (ASCII 8 or HEX 08)
may be used to edit mistakes. AT and A/ may not be
edited. Multiple commands may be placed in the
command line. A command line may be as long as
40 characters, excluding the letters AT. By way of
example, the command below instructs the CH1786
to configure itself to not echo characters when in
command mode E0 and then put itself in answer
mode A.
Enter: ATE0A<CR>
Result: OK
AT Command Set. The available command set is
divided into four types of commands: dial modifiers,
basic commands, ampersand and percent
commands. Refer to the complete list in Table 5.
AT Command Data Rate. With the serial interface,
the rate is speed sensed for parity and format.
THE STATUS MESSAGES
The CH1786 responds with a status message after
each command is executed. This status message
may either be a single digit followed by a carriage
return or a carriage return and line feed with a
message in English, followed by a carriage return and
line feed.
The basic status code subsets are enabled with the
Xn command. Where n=0,1,2,3,4 establishes the
result codes allowed by the user.
X0: Result Codes 0, 1, 2, 3, 4 allowed
X1: Result Codes 0, 1, 2, 3, 4, 5, 10 allowed
X2: Result Codes 0,1, 2, 3, 4, 5, 6, 10 allowed
X3: Result Codes 0, 1, 2, 3, 4, 5, 7, 10 allowed
X4: Result Codes 0, 1, 2, 3, 4, 5, 6, 7, 10 allowed.
NOTE
The CH1786 is factory set to X4, which allows all
result codes.
MODEM STATES
The CH1786 can be in either command mode or data
mode. When the modem is idle, it is in command
mode by default and will recognize commands.
When data transmission is in progress, the CH1786 is
in the data mode state and will not recognize
commands. To force the CH1786 to recognize
commands, the host must send an escape sequence
to the CH1786 forcing it out of data mode and into
command mode.
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 6 Document No. 607-0004 Revision L4 (08/04)
Figure 5. CH1786 Application Diagram
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 7 Document No. 607-0004 Revision L4 (08/04)
Table 2. CH1786 Pin Descriptions
PIN NAME TYPE FUNCTION
1 RING I/O RING. Directly connects to the telephone line’s Ring lead through a user supplied
RJ-11C jack.
2 TIP I/O TIP. Directly connects to the telephone line’s Tip lead through a user supplied RJ-
11C jack.
3 RXA O ANALOG VOICE INJECTED. Receive Signal. Let float if not used. Not active in
CH1786NH.
4 TXA I ANALOG VOICE INJECTED. Transmit Signal. Let float if not used. Not active in
CH1786NH.
5 SPK O SPEAKER. Audio output for speaker. See speaker control schematic in Figure 6.
6 NC - No connection.
7 NC - No connection.
8 SLEEP O SLEEP. A LOW indicates CH1786 is in low power idle mode. Used to control
power to other devices. See Figure 6. Register S24 is the sleep timer register.
When the CH1786 is inactive for a period of time specified by S24, the CH1786 will
power down by about 50% of its normal operating power. During power down, all
I/O lines become undefined. The CH1786 products are shipped from the factory
with a 5 second inactivity timer (ATS24=5) enabled.
9 NC - No connection.
10 TXD I TRANSMIT DATA. Serial Transmit data input. Marking or a binary 1 condition is
transmitted when a HIGH is asserted.
11 RXD O RECEIVE DATA. Serial Receive data output. Received marking or binary 1
condition is indicated by HIGH.
12 V/D O VOICE/DATA. Used to switch between telephone and modem line use. In a typical
application, V/D active HIGH opens the normally closed voice injection relay and
disconnects the handset from the telephone line. HIGH indicates the CH1786 is off-
hook and online. Therefore, this pin also reflects the state of the off-hook relay of
the CH1786. See Figure 2.
13 DTR I DATA TERMINAL READY. Active LOW. Switching off DTR can either return
modem to command state, disconnect phone call, or reset modem. DTR should be
set LOW when not used.
14 DSR O DATA SET READY. LOW indicates handshaking with a remote modem is in
progress, and/ or the data carrier of a remote modem has been detected.
15 RI O RING INDICATION. This signal follows the frequency of the ringing signal and is
normally about 20 to 40 Hz for 2 seconds on with 4 seconds off.
16 CTS O CLEAR-TO SEND. Ground if not using the FAX option. Reserved for flow control
when using FAX option. CTS only active on CH1786 when S24=255.
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 8 Document No. 607-0004 Revision L4 (08/04)
Table 2. CH1786 Pin Descriptions Continuation
PIN NAME TYPE FUNCTION
17 DCD O DATA CARRIER DETECT. LOW indicates a data carrier from a remote modem is
detected. Must be enabled using the &C1 command.
18 HS O SPEED INDICATION. HIGH speed select output. A low on this pin indicates the
modem is operating at 2400bps.
19 VCC - POWER SUPPLY. 5 volts + 5% Note: Noise should be less than 50mV peak to
peak.
20 GND - GROUND. Note: Noise should be less than 50mV peak to peak.
21 RST1 I RESET. Active HIGH. This input must be asserted HIGH for at least 10 ms to reset
the modem. RESET is then returned LOW for normal operation. If no system reset
is available, let this pin float to enable internal reset.
22 NC - No connection required. For CH179X or CH2056 compatibility, connect to GND or
use as an active LOW input for request to send (RTS) functionality for CH179X/2056
products.
Note: (1) If VCC has a slow power up ramp time, the internal reset may be ineffective.
(2) Do not drive LED’s directly from any output. Use Buffers.
Table 3. Summary of Result Codes and Meanings.
Result Codes Status Message Meaning
0 OK Command Executed
1 CONNECT Carrier detected at 300bps
2 RING Ring Detected
3 NO CARRIER Did not detect carrier
4 ERROR Entry error
5 CONNECT 1200 Carrier detected at 1200bps
6 NO DIAL TONE Off-hook, but no response after 5 seconds
7 BUSY Busy signal detected
10 CONNECT 2400 Carrier detected at 2400bps
The escape sequence consists of a “guard time” (a
period where no characters are sent to the modem),
followed by 3 escape characters, followed by another
guard time. The guard time is set by register S12.
The escape character code is set in register S2. At
power-up, the guard time is set to 1 second minimum,
and the escape character is set as “+.” There is no
minimum delay between characters but the maximum
delay is set by register S12.
The CH1786 will stay off-hook with its carrier on after
the escape sequence is received. It will return an OK
status message when it is ready to accept
commands. The CH1786 may be put into data mode
by issuing the command ATO<CR>.
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 9 Document No. 607-0004 Revision L4 (08/04)
AT COMMAND APPLICATIONS
Dialing A Phone Number. The Dial command takes
the form Dn, where n is a string of characters. In the
simplest form, n will be only the digits of the phone
number to be dialed.
Example: Tone Dial number.
Enter: ATD1234567<CR>
Result: OK
In response to this command, the CH1786 dials the
telephone number “123-4567” and then waits for a
carrier from the distant modem. If no carrier is
detected within a given time (the default time is 30
seconds), the CH1786 automatically releases the line
and sends a NO CARRIER result code. If a carrier is
detected, the CH1786 gives a CONNECT result code
and goes on-line, permitting communication with the
distant modem.
The Dial Command may also be issued without a
telephone number. ATD causes the modem to pick
up the telephone line without dialing a number.
Pause During Dialing. When placing a call from an
office with a telephone connected to a PBX, it may be
necessary to dial an access code (usually the digit 9)
to get an outside line. Inserting a comma in the
telephone number instructs the modem to pause for a
specific length of time. The factory set default pause
time is 2 seconds.
Example: Pulse Dial 9,pause, dial number.
Enter: ATDP9,1234567<CR>
Result: OK
Multiple commas may be used to generate integer
multiples of the specified delay time.
Originate a Call in Answer Mode. The D command
forces the modem into originate mode. To call an
originate-only modem, dial the number and set the
modem to answer mode via the R command (reverse
originate). This is done by including an R at the end
of the telephone number.
Example: Change modem from original-only to
answer mode.
Enter: ATDT1234567R<CR>
Result: OK
Multiple commas may be used to generate integer
multiples of the specified delay time.
Redial Last Number. The repeat command is a
convenient way to execute the previously entered
command line.
Example: Use A/, the repeat command, to redial the
last telephone number dialed.
Enter: A/
Result: ATDT1234567R<CR> Previous command
OK line executed
Return to Command State. Use ; to return to
command mode offer dialing.
Example: Touch-tone dial 9, pause, dial number,
return to Command.
Enter: ATDT9,1234567;<CR>
Result: OK
Automatic Answering. The SO register controls the
number of rings that must occur before the modem
answers a call. The register may range in value from
0 to 255.
S0 = 0 DO NOT ANSWER TELEPHONE
S0 = 1 ANSWER ON RING 1
S0 = 2 ANSWER ON RING 2
S0 = 3 ANSWER ON RING 3
S0 = 255 ANSWER ON RING 255
When S0 is set to 0, the modem will not auto-answer.
The Serial Interface Lines. The CH1786 supports a
full EIA-232D/V.24 serial interface. Signal levels are
TTL rather than EIA-232D level compatible, which
allows direct connection of the CH1786 to the host
UART without the need for level translation circuitry.
See Table 2 for a complete pin description.
The CH1786 is controlled by sending it serial
commands over TXD and its status determined by
monitoring the serial status messages returned on
RXD. DTR is optionally used to reset, terminate calls
or return CH1786 to command mode.
All other serial interface lines may be utilized for the
convenience of a particular application but are not
required by the CH1786. Unused outputs (from
modem) should be left unconnected. Unused inputs
should be set to the proper logic level. See Table 2.
Fax Modes. The CH1786 Product Family supports
Send and Receive FAX. The modes and rates are
determined by the AT+F commands. Refer to Table
6A.
FAX modem processing is explicitly defined in ITU-U
V.29, ITU-U V.27, and ITU-U V.21 recommendations.
All modulation, wave-form spectrum, and data
processing functions conform to the appropriate
specifications.
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 10 Document No. 607-0004 Revision L4 (08/04)
Table 4. S-Register Summary.
Register
Description
Range
Units
Saved
Firmware
Defaults
Factory
Defaults
S0 Ring to Answer On 0-255 rings * 000 001
S1 Ring Count 0-255 rings 000 000
S2 Escape Code Character 0-127 ASCII 043 043
S3 Carriage Return Character 0-127 ASCII 013 013
S4 Line Feed Character 0-127 ASCII 010 010
S5 Back Space Character 0-32, 127 ASCII 008 008
S6 Maximum Wait Time for Dial Tone 2-255 s 002 002
S7 Maximum Wait Time for Data Carrier 1-255 s 030 030
S8 Pause Time for Comma 0-255 s 002 002
S9 Carrier Detect Response Time 1-255 1/10s 006 006
S10 Lost Carrier to Hang-up Delay 1-255 1/10s 014 014
S11 DTMF Dialing Speed 50-255 ms 095 095
S12 Escape Code Guard Time 0-255 1/50s 050 050
S13 Reserved - - - 000 000
S14 Bit Mapped Options Register Bit Mapped none * 170 (AAH) 170 (AAH)
S15 Reserved - - - 000 000
S16 Modem Test Options Bit Mapped none 000 000
S17 FAX Mode Null Byte Timer 0-255 4ms incr 000 000
S18 Test Timer 0-255 s * 000 000
S19 Protocol Interface Speed 0-1 none 000 000
S20 FAX Mode Inactivity Timer 0-127 s 000 000
S21 Bit Mapped Option Register Bit Mapped none * 000 096 (06H)
S22 Bit Mapped Option Register Bit Mapped none * 118 (76H) 118 (76H)
S23 Bit Mapped Option Register Bit Mapped none * 007 (07H) 023 (17H)
S24 Sleep Mode Inactivity Timer 0-255 s 000 000
S25 Delay to DTR Off 0-255 0.1 or 1s * 005 005
S26 RTS to CTS Delay Interval 0-255 0.01s * 001 001
S27 Bit Mapped Option Register Bit Mapped none * 064 (40H) 064 (40H)
S28 Bit Mapped Option Register Bit Mapped none * 000 001
NOTES: 1. Parameters indicated with a (*) in the Saved column may be stored in User Profile n=0, 1 by executing
the appropriate &Wn command.
2. A stored Profile is a subset of allowed parameters and is comprised of those parameters displayed
with the &V command.
3. Factory Default values that are different from the Firmware Default values are highlighted in BOLD.
4. Restore Factory Default values using Zn command.
5. Restore Firmware Default values using &Fn command.
NOTE
The CH1786LC and CH1786NH products do not contain NVRAM and, therefore, do not support data storage after
power down. A detailed definition of all commands and S-Registers is available from Cermetek Microelectronics,
Inc. Refer to Cermetek Document AT Commands and S-Registers Reference Guide or access our website at
www.cermetek.com.
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 11 Document No. 607-0004 Revision L4 (08/04)
Table 5. CH1786 AT Command Set Summary.
Basic
Commands
Function
AT Attention Code
A Answer command
A/ Repeat last Command
Bn* Communications Standard Option
D Dial Command
E* Off-Line Character Echo Option
Hn Switch Hook Control Option
Ln* Speaker Volume Option
Mn* Speaker Control Option
On On-Line Command
Qn* Result Code Display Option
Sn Select an S Register
Sn= Write to an S Register
Sn? Read an S Register
Vn* Result code Form Option
Xn* Result Code Set/Call Progress
Option
+++ Escape Sequence
, Pause
? Returns Last addressed S-Register
Yn* Long Space Disconnect Option
Fn On Line Echo character Option
Zn Restore Active Profile
Table 6A. FAX Command Set Summary.
FAX Command Function
+FCLASS=n Select Service Class
+F<command>? Report Active Configuration
+F<command>=? Report Operating Capabilities
+FAA=n Data/Fax Auto Answer
+FF Enhanced Flow Control
+FTS=n Stop Transmission and Wait
+FTM=n Transmit Data
+FTH=n Receive Data
+FTH=n Transmit Data with HDLC
Framing
+FRH=n Receive Data with HDLC
Framing
+FRT=n Receive Test Data
+FTTn=m Transmit test Data
Table 6B. Dial Modifiers Summary.
Dial Modifiers Function
P Pulse Dial
R Originate Call in Answer Mode
T Touch Tone Dial
W Wait for Dial Tone
; Return to Idle State
@ Wait for Quiet Answer
Command
! Flash Hook
, Pause
0-9
A,B,C,D, #, *
Allowed Dial Digits/Characters
Table 6C. Ampersand and Percent Commands.
Ampersand
Commands Function
&Cn* Data Carrier Detect Option
&Dn* Data Terminal Ready Option
&Fn Restore Active Profile
&Gn* Guard Tone Option
&Pn* Make to Break Ratio Section
&Sn* Data Set Ready Option
&Tn Test Command Option
&V View Active Configuration
&Wn* Store Active Profile
&Yn* Set Profile to be used after hard
reset
&Zn* Store Telephone Numbers
PHONE LINE CONNECTION GUIDELINES
1. The CH1786 must be mounted in the final
assembly such that it is isolated from exposure to
any hazardous voltages within the assembly.
Adequate separation and restraint of cables and
cords must be provided.
2. The circuitry from the CH1786 to the telephone
line interface must be provided in wiring that
carries no other circuitry other than that
specifically allowed in the FCC rules (such as A
and A1 leads).
3. Connection to phone line should be made
through an RJ-11C jack.
4. PCB traces from the modem’s RING and TIP pins
to the RJ-11C jack must be 0.1 inch spacing or
greater to one another and 0.2 inch spacing or
greater to all other traces. The traces should
have a nominal width of 0.020 inches or greater.
5. The RING and TIP PCB traces should be as
short as possible and oriented to prevent
coupling other high speed or high frequency
signals present on the host circuit PCB.
6. No additional circuitry other than that shown in
Figure 7A or 7B may be connected between the
modem module and the RJ-11C jack. Doing so
will invalidate the FCC approval.
7. The CH1786LC, and CH1786NH (only) requires
external surge protection (see Figure 7B). This is
mandatory to maintain FCC Part 68 conveyed
approval.
8. The CH1786, the RJ-11C jack, the interfacing
circuitry and all PCB traces in between, must be
contained on a PCB with a 94 V-0 flammability
rating.
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 12 Document No. 607-0004 Revision L4 (08/04)
9. The supplied FCC registration label must be
applied visibly on the outside of the product.
10. The product’s User Manual must provide the user
with instructions for connection and use as
recommended in the FCC Registration Section
below.
CH1786 HANDLING AND ASSEMBLY
RECOMMENDATIONS
The CH1786 contains static-sensitive components
and should only be handled by personnel and in
areas that are properly protected against static
discharge. The two recommended mounting
techniques for physically connecting the CH1786 to a
PCB are discussed below.
Figure 6. Speaker Control Circuit: Optional to
allow for call progress monitoring.
Direct Soldering. The CH1786 may be wave
soldered. All CH1786 products are hermetically
sealed (except the CH1786NH) and will not be
harmed by industry standard wave soldering
processes. Cermetek recommends against exposing
the non-hermetic CH1786NH to aqueous based
rinsing processes.
Socketing. The socketing approach to mounting
eliminates cleaning and desoldering concerns. When
the socket is used, it must make a solid connection to
all pins. Failure to do so will cause unreliable or
intermittent operation. Also, steps should be taken to
assure that the module remains tightly seated in the
socket during shipping. Cermetek recommends using
sockets from Samtec. See Application Note # 130,
Summary of Recommended Suppliers.
FCC REGISTRATION
All products in the CH1786 family are registered with
the FCC (Federal Communications Commission)
under Part 68. To maintain the validity of the
registration, you must serve notice to the end user of
the products of several restrictions the FCC places on
the modem and its use.
In addition to restriction notification, the FCC requires
that Cermetek make all repairs to all products in the
CH1786 family. If repairs are necessary after
installation of the CH1786 in the end product and the
end product has been delivered to the end user, the
end product must be returned to the end product
supplier where the CH1786 can be removed and then
forward to Cermetek for repair. The following notice
is recommended and should be included in the end
product’s user manual.
FOR YOUR USER’S MANUAL
The FCC Part 68 rules require the following (or
equivalent) be provided to the end user of equipment
containing a DAA.
Type of Service. The (insert end product name) is
designed to be used on standard device telephone
lines. It connects tot he telephone line by means of a
standard jack called the USOC RJ-11C (or USOC
RJ45S). Connection to telephone-company-provided
coin service (central office implemented systems) is
prohibited. Connection to party lines service is
subject to state tariffs.
Changes in Attestation Procedure for Plugs and
Jacks. (Name of applicant) attests that the network
interface plugs or jacks used on this equipment
comply with and will continue to comply with the
mechanical requirements specified in Part 58, sub-
part F, specifically the dimensions, tolerances and
metallic plating requirements. The compliance of
these connectors will be assured by purchase
specifications and incoming inspection.
Documentation of such specifications and/ or
inspections will be provided to the FCC within 30
days of their request for the same.
Telephone Company Procedures. The goal of the
telephone company is to provide you with the best
service it can. In order to do this, it may occasionally
be necessary for them to make changes in their
equipment, operations or procedures. If theses
changes might affect your service or the operation of
your equipment, the telephone company will give you
notice, in writing, to allow you to make any changes
necessary to maintain uninterrupted service.
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 13 Document No. 607-0004 Revision L4 (08/04)
In certain circumstances, it may be necessary for the
telephone company to request information from you
concerning the equipment which you have connected
to your telephone line. Upon request of the
telephone company, provide the FCC registration
number and the ringer equivalence number (REN);
both of these items are listed on the equipment label.
The sum of all of the REN’s on your telephone lines
should be less than five in order to assure proper
service from the telephone company. In some cases,
a sum of five may not be useable on given line.
Consult your telephone provider.
If Problems Arise. If any of your telephone
equipment is not operating properly, you should
immediately remove it from your telephone line, as it
may cause harm to the telephone network. If the
telephone company notes a problem, they may
temporarily discontinue service. When practical, they
will notify you in advance of this disconnection. If
advance notice is not feasible, you will be notified as
soon as possible.
When you are notified, you will be given the
opportunity to correct the problem and informed of
your right to file a complaint with the FCC. Contact
your local telephone service provider if you have nay
questions about your phone line.
In the event repairs are ever needed on the (insert
your product name), they should be performed by
(insert your company name) or an authorized
representative of (insert your company name). For
information contact: (insert your company address).
DEFAULT STATUS, PERFORMANCE, AND
SPECIFICATIONS
The following is a summary of the Default
Configuration Profile installed by Cermetek
Microelectronics, Incorporated, prior to delivery
of the CH1786.
Async mode selected
2400bps
Bell 212A operation at 1200bps
Even parity
Auto answer enabled (Disabled on CH1786NH)
Command echo ON
All result codes enabled –extended
Wait for dial tone before dialing =2 seconds
Detects busy signal
Full word result codes
Pulse dial make/break ratio =39/61
DSR enabled
Modem ignores DTR
DCD enabled (Disabled on CH1786NH)
Speaker enabled but off when receiving carrier
Speaker volume set to medium
Local modem will grant RDL request from remote
modem
Guard tones disabled
Minimum DTR pulse width =0.1 seconds
Ring count =01 (CH1786)
Escape code character =43
Carriage return character =13
Line feed character =10
Back space character =08
Duration of wait for dial tone =02 seconds
Duration of wait for carrier after dialing =30 seconds
Duration of dial pulse (comma)=02 seconds
Carrier detect response time =0.1 seconds
Escape code guard time =1 second
Length of use after comma =2.0 seconds
Last carrier to hang up delay =0.1 seconds
DTMF interdigit delay =0.1 seconds
DTMF Attenuation =-4dB
Sleep mode inactivity time =5 seconds
Long space disconnect disabled
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 14 Document No. 607-0004 Revision L4 (08/04)
1. Currently Limiting PSTN Protection Line
Device.
Currently limiting devices are mandatory to meet
UL safety standards. To maintain conveyed FCC
Part 68 approval, the current limiting components
identified as F1 and F2 in dashed Box #1 must
also survive FCC Part 68 surge testing. Refer to
Cermetek Application Note #126, Supplemental
PSTN Line Protection, for more details. Refer to
Application Note # 130, Summary of Recommend
Suppliers, for a list of suppliers and associated
part numbers.
A resettable/repairable fuse (rated at 0.15 amps)
is preferred because it resets automatically upon
removal of the current flow. Non-resettable
devices are also acceptable. Although CSA CS-
03 Part 1 (Canada) follows the requirements of
FCC Part 68 (USA), Cermetek recommends
contacting DOT (Canada) and/or a certified
independent lab to verify compliance.
2. PSTN Current Limiting Resistors.
Low value (10) carbon film 1/4 watt resistors may
be required (identified as R1 and R2 in dashed
Box 2), depending on end product application
environment, to enhance performance by reducing
susceptibility to PSTN current surges that may
occur before the OVERVOLTAGE PROTECTION
device (identified as D1 in dashed Box 3)
becomes fully activated.
Refer to Cermetek Application Note # 130,
Summary of Recommended Supplies, for a list of
suppliers.
3. Over Voltage and Lightning Protection.
Surge Protection is provided by internal circuitry
contained within all CH1786s (except CH1786NH).
No additional external components are required to
maintain conveyed FCC Part 68 approval for all
CH1786s Products (except CH1786NH). External
protection as indicated in dashed Box 4 MUST BE
included when using CH1786NH products.
4. Optional External Over Voltage and Lightning
Protection.
In most environments, the internal two terminal
surge suppressor (see dashed Box 3) is adequate.
For severe environments, use an external three
terminal device with an earth ground as is shown
in dashed Box 4.
5. EMI/RFI Suppression.
EMI/RFI suppression is recommended. This is for
obtaining FCC part 15 A and/or B. It is also used
to suppress external EMI / RFI signals that can
affect modem operation, such as strong radio
signals, should the modem be near a source of
such signals. No external EMI/RFI noise
suppression circuitry is required to maintain
conveyed FCC Part 68 approval. Additional
suppression may be added as described below
without adversely affecting FCC Part 68 approval.
A. To provide adequate EMI/RFI suppression,
the capacitor/inductor network contained in
dashed Box 5 should be located as close to
the RJ-11C Jack as possible. Further, this
network should be provided with an excellent
ground path to the chassis.
B. Capacitors C1 and C2 should not exceed
0.005µf. They must have a rating of 1.5KV
and typically are 0.001µf ± 20%. Inductors L1
and L2 may be either individual inductors or a
dual inductor. Refer to Application Note #130
for a complete list of recommended vendors
and associated part numbers. For UL
applications, choose capacitors and inductors
that are UL 1950 listed. The actual values of
the components used may vary depending on
the end product design and the nature of the
EMI/ RFI. Consult an FCC part 15 consultant
if required.
Figure 7. PSTN Line Interface for all CH1786 Products.
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 15 Document No. 607-0004 Revision L4 (08/04)
Table 7. CH1786 System Data Mode Compatibility Specifications.
Parameter Specification Parameter Specification
Asynchronous 2400, 1200 600 bps character
asynchronous.
0-300 bps asynchronous
Receive Carrier
Frequencies
V.22 bis, V.22,
212A
Originate 2400Hz ± 7Hz
Answer 1200Hz ± 7Hz
Asynchronous Speed
Range
TXD may differ +1%, -2.5%
from modem output. Offsets
will be corrected by adding/
deleting stop bits.
Bell 103 Answer ‘space’ 2020Hz ±
7Hz
Answer ‘mark’ 2225Hz ±
7Hz
Originate ’space’ 1070Hz ±
7Hz
Originate ‘mark’ 1270Hz ±
7Hz
Asynchronous Format 8,9,10 bits, including start,
stop, parity.
Receiver
Sensitivity
OFF to ON threshold –43 dBm
ON to OFF threshold –48 dBm
Telephone Line Interface Two-wire full duplex over
public switched network. On-
chip hybrid and billing delay
timers.
Billing Delay 2.0 to 3.0 seconds (Ta=25°C)
Modulation V.22 bis, 16 point QAM at 600
baud. V.22 and 212A, 4 point
DPSK at 600 baud. 103
Binary phase coherent FSK.
Hysteresis 2 dB minimum
Self Test Pattern
Generator
Alternate ‘ones’ and ‘zeros’
and error detector, to be used
along with most loopbacks. A
number indicating the bit
errors detected is sent to DTE.
Line
Equalization
Fixed compromise
equalization, transmit.
Adaptive equalizer for
PSK/QAM, receive.
Transmit Carrier
Frequencies V.22 bis,
V.22, 212A
Originate 1200Hz ± .01%
Answer 2400Hz ± .01%
Diagnostic
Available
Local analog loopback.
Local analog loopback.
Remote digital loopback.
Request remote digital
loopback.
Local interface loopback
modem with self-test.
Bell 103 Originate ’space’ 1070Hz ±
.01%
Originate ‘mark’ 1270Hz ±
.01%
Answer ‘space’ 2020Hz ±
.01%
Answer ‘mark’ 2225Hz ±
.01%
Call Progress
Tones Detected
Computer
Interface
With speaker or quiet screen
messages (No dial tone, busy,
ring-back, modem answer tone
and voice).
IBX PC/XT/AT bus compatible
with an 8250/16450/16550A
UART as a serial controller.
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 16 Document No. 607-0004 Revision L4 (08/04)
Table 8. CH1786 Electrical Specifications.
Parameter Description Min. Typ. Max. Units
VCC Positive Supply Voltage- Noise less than 50mV 4.75 5.0 5.25 V
ICC Off Hook Nominal Operating Current when modem is OFF Hook 50 75 mA
ICC On Hook Nominal Operating Current when modem is ON Hook 25 50 mA
ICCPD Power Down Current 10 mA
VIH High Level Input Voltage* 2 V
VIL Low Level Input Voltage* -0.3 0.8 V
IIN Input Leakage Current (TXD, DTR, RTS) 15 100 uA
ILO Leakage Current DCD, HS, RXD, SLEEP, DSR 10 uA
CP Capacitive Lead (TXT, DTR, RST) 10 pF
VT+ Positive Hysteresis Threshold for RESET pin 2.5 V
VT- Negative Hysteresis Threshold for RESET pin 1.8 V
VOH High Level (IOH = 0.5mA)* 2.4 V
VOL Low Level (IOL = 1.6mA)* 0.6 V
Test conditions: VCC = 5V ± 10%, Temp = 0°C to 70°F (unless otherwise stated).
*Output Load = 50 pF ± one TTL.
Table 9. CH1786 Electrical Specifications.
Parameter Minimum Typical Maximum Units Comments
Off Hook Impedance 20 Ohms
Trans Hybrid Loss 25 dB 600 Ohm, RXA, TXA
Ring Voltage Loop 75V 250V Vpp On 48VDC line voltage for
sustained periods
Line Loop Current-(Off-
Hook)
20 100 mA
Return Loss @ 1000Hz 15 dB 600 Ohm
Ring Frequencies 40 Hz
Receiver Insertion Gain -0.5 0.0 +0.5 dBm 600 Ohm- Data Mode
Transmit Power -9.5 dB
First Character After Reset 0.5 1.0 5 sec Delay
Inter Character Delay 20 50 msec Between all command
characters
Command Delay 100 200 msec Between all AT commands
Minimum Reset Pulse
Duration
10 msec If user supplied
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 17 Document No. 607-0004 Revision L4 (08/04)
Table 10. Other Performance Specifications.
Parameter Minimum Typical Maximum Units Comments
Tone 2nd Harmonic
Distortion
-35 dB HYB enabled into 600
DTMF Twist (Balance) 3 dB
DTMF Tone Duration 50 255 ms 95ms default
Pulse Dialing Rate 8 10 20 pps 10pps default
Pulse Dialing Make/
Break
39/61 % US, Canada default
Pulse Dialing Make/
Break
33/67 % UK, Hong Kong
Pulse Interdigit
Interval
700 3000 ms 789ms default
Guard Tone
Frequency
550 Hz Referenced to High Channel
Transmit
Guard Tone Amplitude -6 dB Referenced to High Channel
Transmit
Guard Tone
Frequency
1800 Hz Referenced to High Channel
Transmit
Guard Tone Amplitude -9 dB Referenced to High Channel
Transmit
High Channel
Transmit Amplitude
-1 dB Referenced to Low channel,
Guard tone enabled
Guard Tone 2nd
Harmonic Distortion
-40 dB
Call Progress
Passband Frequency
120 620 Hz
Wait Time for Dial tone 2 255 sec Two second default
Return loss @ 1000Hz 30 dB Tr=600 + 2.16 µF
Table 11. Analog Characteristics.
Name Type Characteristic Value
SPK O(DF) Minimum Load
Maximum Capacitive
Load
Output Impedance
Output voltage
D.C. Offset
300
0.01µ
10
2.5± 1.6V
<20mV
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 18 Document No. 607-0004 Revision L4 (08/04)
Table 12. CH1786 Pin Functions.
PACKAGE CONNECTION TABLE
PIN NO. FUNCTION PIN NO. FUNCTION
1 RING 12 V/D
2 TIP 13 DTR
3 RXA 14 DSR
4 TXA 15 RI
5 SPK 16 CTS
6 NC 17 DCD
7 NC 18 HS
8 SLEEP 19 VCC
9 NC 20 GND
10 TXD 21 RST
11 RXD 22 NC
Figure 8. CH1786 Physical Dimensions.
Cermetek Microelectronics, Inc. CH1786 Family of Ultra Small 2400bps Modems
2004 Cermetek Microelectronics, Inc. Page 19 Document No. 607-0004 Revision L4 (08/04)
Table 13. Summary CH1786 Family of Products.
Model
Summary of Features
Operating
Temperature
CH1786 Full function, Voice/Inject, NVRAM, FCC Part 68 approved, UL 1950
Listed, Hermetic
0°C to 70°C
CH1786ET Full function, Voice/Inject, NVRAM, Zero Power Option, FCC Part 68
Approved, UL 1950 Listed, Hermetic
-40°C to 85°C
CH1786FX Full function, FAX, Voice/Inject, NVRAM, FCC Part 68 approved, UL
1950 Listed, Hermetic
0°C to 70°C
CH1786LC Full function, Voice/Inject, FCC Part 68 Approved, UL 1950 Listed,
Hermetic
0°C to 70°C
CH1786NH Full function, FCC Part 68 Approved, Non-Hermetic, Listed UL 1950 0°C to 70°C
Cermetek reserves the right to make changes in specifications at any time and without notice. The information furnished by
Cermetek in this publication is believed to be accurate and reliable. However, Cermetek assumes no responsibility for its use, or for
any infringements of patents or other rights of third parties resulting from its use. No license is granted under any patents or patent
rights of Cermetek.
Cermetek provides the user with a FCC/DOT Approved or Approvable device. However Cermetek does not have influence or
knowledge of Application environment. Therefore, for FCC Approved or Approvable devices, the user assumes all risk for
maintaining compliance to registration.
Printed in U.S.A
406 TASMAN DRIVE | SUNNYVALE CA 94089 | LOCAL: 408-752-5000 | TOLL FREE: 1-800-882-6271 | FAX: 408-752-5004
CERMETEK WEB SITE: http://www.cermetek.com | EMAIL: sales@cermetek.com
iModem Network WEB SITE: http://www.imodem.net/ or https://sunnyvale.imodem.net/
