3 Watt Cell Modem

ACMM 900-3W 3 Watt Cellular modem
ACMM 900-3W is a low power 3 watt solution for packet data communications over AMPS network .

The Cellular Modem Module, ACMM 900-3W, uses the Advanced Mobile Phone System (AMPS) cellular network for data transmission. AMPS is the cellular system used in North America, Latin America, Australia, New Zealand and parts of Africa. AMPS system is not compatible with the digital systems, such as GSM, PCS or CDMA.

  • AMPS Circuit Switched Cellular network
    for data transmission

  • Modem "AT" command set

  • Choice of  TTL or RS 232 serial interface

  • For embedded applications

  • Choice of Hardware or Software Flow Control

  • Incorporates "Quiet Mode" thereby enabling communication with "non-intelligent" systems



The ACMM 900-3W is a low power solution for packet data communications over AMPS network . It is ideal for monitoring of pressure, temperature, liquid level, flow, etc. in industrial and commercial applications. The Cellular Modem Module ACMM 900-3W acts as a standard RS 232 "AT" command compatible modem. This allows compatibility with popular software packages such as Procomm, HyperTerminal, Bitcom, Winfax, etc.

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Example applications for data communications with ACMM 900-3W include:

Unit includes:


What you need to provide:

Registering the Cellular Modem Unit:

To register your cellular modem unit, do the following:

The cellular operator will register your unit and provide you the following information:


Cellular Modem Module (AMPS)

Date Rate Upto 9600 bps
Data Compression MNP 2-4, MNP 5, V42.bis
and Error Correction MNP 10
DTE Rate Upto 57600 bps (switch selectable)
Transmit Power 3W
Interface RS 232 Asynchronous
Signals Supported TXD, RXD, CD, DSR, RTS, CTS
Power Supply 12V @ 1.5 A
Mechanical 4.5 x 2 x 1 inches L x W x H)
Environment -10 to +70 C
Humidity 90% non-condensing
Custom Options Yes
Ordering Information
ACMM 900-3W (3W option)



Q1: What is the flow control method recommended?

A1: If the host is a PC, Hardware flow control is recommended.

However, in most control instrumentation, either software or no flow control is called for.

Q2: How do I disable any flow control?

A2: Simply disable both the Hardware and software control switch settings. This is not recommended for large file transfers.

Q3: I need to connect the Cellular Data Link to a machine, which does not understand your messages.
      All it needs is data. Which configuration is


A3: Please use the ATQ1&w&w1<CR> command.

Q4: Have you experienced unreliable communication with certain modems?

A4: Yes. Several generic brands tend to throw hot signals (i.e. strong signal levels) on the line. This causes the cellular service to over-modulate, which leads to distortions and results in unreliable connections.

Q5: What is the solution?

A5: We recommend that you use modems that support MNP-10 and also allow transmit level to be reduced to between 15 dbm 20 dbm. Rockwell based modem designs generally meet these requirements. For Rockwell based modems, please try the following commands on the land line modem:

AT-SEC=1,18 <CR>. This will enable MNP 10 and set transmits level to 18 dbm.

AT+MS=11,1,1200,2400X3&W&W1<CR>. Sets the modem to communicate between 1200 and 2400 bps.

Q6: Is there any simple way to avoid frequent loss of connection?

A6: Please program the CMM 900-3W as follows AT+MS=11,1,1200,1200&W&W1<CR> This will force the CMM 900-3W to connect only at 1200 bps.

Q7: What initialization string is recommended to communicate with non-MNP modems?

A7: Connection with non-MNP landline modems is not recommended.

Q8: Is there any recommended init string for various land line mode.

A8: The following have been tried with excellent results.
a) For US Robotics / 3 Com modems:

ATS10=200&A3&B1&N2&U2&W&W1 <CR>

b) For Rockwell chip set based land-line modems 33600 and lower

AT%E2\N2S7=60S10=200+MS=11,1,1200,2400&w&w1 <CR>

c) For most other brands:

ATN0S37=6S10=200&w&w1 <CR>

d) For Rockwell chip set based land-line modems 56K V90 models AT%E2\N2S10=200S7=60+MS=V34,1,1200,2400,1200,2400 <CR>

Q9: My requirement (s) are totally unique. Do you offer custom solutions?

A9: Yes.

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