GSM MODEM FAQ Especially for Wavecom GPRS modem.


Question: Are the all GSM-modems equal?


No! They may seem equal from outside, but if you look carefully, they are quite different.
They use different power supplies. Most use DC 5-to- 32V input. They are suitable for trucks, cars and domestic use.
The power supply connector may be a special one or normal 5.5mm outside 2.5mm inside power plug.
External power supply 230AC/DC is need for office use. 12 DC 600 mA is a suitable value for the most of the modems.

The data connection must fit to PC DB9, but how connect audio signals? They need as special DB15 connector and adapter cable
for the PC and audio. Normally audio is not available, but only the most advanced modems.
Some modems has a mprobyte.fil case and fixing supports to the installation cabinet.
PC connector names: images.jpegIXbrick.serialport.pinouts.gif9-pinout.gifimages.jpeg

Question : How about antenna connectors, are they equal?


No. Some use FME , male or female connectors, some use SMA male or female ( reverse or normal or pin or no pin)
Anyway the most GSM-modems use external antenna.
If the installation is done to an electrical cabinet, the antenna must be installed outside.
Normally 2m cable is enough.
Some USB-modem use integral ceramic-antenna like GSM-phones.

rp SMA MALE ( rp = reverse polariry)
rp SMA FEMALE ( rp = reverse polariry)

Question : I want to use GSM modem with PC, do I need driver for the modem?

No, if you have a DB9 serial port in your PC. Just any terminal program can operate modems. If our portable PC has no serial port, you need a USB/RS232 converter and driver CD ( or find a driver from the internet).
RS232/USB converter finds

Question : I installed a USB/RS232 converter. It worked yesterday, but not any more. Is the converter broken?

No, You put the the USB connector to different one. You have now more COM-port installed, but only one is working . Please look Control Panel/ Hardware/Com-ports section. Use only one mechanical port for modems.

Question : My modem do not answer to AT- command? Is it broken?


Probably not. Different modems use different baud rates at defaults.
Some common are 9600, 19200 and 115200 baud( WQ24 modem ).
Test these first with AT<cr> command and then change to your speed eg.

Change your terminal speed to 9600 baud and save the new speed

Look Wavecom AT-commands:

Question : What is the input voltage range of the Wavecom GPRS modem?

It is same as Maestro 100 Lite 5- 32V. It suits for 5,12, and 24V systems.

Question : Where I found technical manual and AT-command manual?


Wavecom support pages:
Sierra Wireless pages require registration
AT command manual is available here :

WQ24 GPRS modem technical data:

Question : My modem is installed into metal cabinet. How I connect antenna ?


Use SMA extension antenna with magnetic base

Question : How I connect modem to my control cabinet ?


In the packet there are two metal clips, which suits for the holes in the modem.

Modem clips ia put to backside of modem


Look the picture. The modem can connected directly to DIN -rail using M4 screws, external DIN clips or square nuts to C-rails.
There are many possibilities to install light (120g) GSM modem.
Other type of DIN Clip


Question : How I do program the GSM -modem?


There are no programming needed, but you must know how to operate the modem to do the task what you want.
The commands are done by a AT-commands like in old wire modems. PC/XP has a Hyperterminal program. It can be used to send commands to modem.
E.g. send a ready made SMS -message from memory #1

You can start teach yourself for GSM-commands and programming by reading a GSM Driver CD (from :

It has programming examples for PC and micro controllers.
AT-command are explained in detail.
Error codes are explained.

It has 49 pages. All normal commands are expalained.
Also normal ( wire) modems are axplained.
There are PCB, schematics, and programm explaned.


A humidity sensor send a SMS-message


We can help to make a suitable program.
Some application do not need any device, just connect the external alarm relay to Wavecom modem. Look the picture above .

Question : How I do insert a SIM card ?


Push a small button near SIM card. Note how to insert card in the picture.
Remember to take PIN number asking off with your own GSM phone or you have give right PIN number each time before you connect power to the modem.


Question : How much this modem costs?


Question How I send SMS message ?

Answer: First put the modem on text message mode
then write the message

AT+CMGW=”+358445661885”,145<CR> use international mode ( +358 = Finland).
AT+CGMG="04412345678",129<CR> local phone number format
Some modems do not need 145 or 129 parameters
The modem gives a prompt
write data eg. Alarm now
At end give <CNTRL/Z>

Question How I send an alarm with a contact ?

This command works Wavecom modem.
Wavecom modem can make a simple alarm device with only one contact with a DB9 putting pins 7 and 8 (CTS) together
or connect +12V voltage to pin 8

First enable this function
AT%D2 <cr>
AT&W <cr> save to EEPROM

SMS message sending is successful when the DTR signal rises (pin 4 -> 12 V).

SMS message # 1 must be made ​​ready.
First remove old message ( if available )
AT+CMGD=1 <cr>

Write a new one
AT+CMGW = "+35832661885", 145 <cr>

Pils water high

These commands must be put at right seqenece


Question I need vandal proof GSM antenna for Car wash payment units

Answer look this BH0012 GSM antenna. It has 2 m cable. a M12 fixing to roof. From outside it is difficult to open


Question- How I control water from remote place ( 2 km) to get snow ?


You need two modems. One for measuring the reservoir and one to control the pumps.
You need four level sensors to measure water. Then you send water level to other GSM-moden, which controls the pump.

Look the picture below. Thus is done in Ylläs/Finland 2013.


Picture from Ylläs Ski resort Finland


How I can read Maestro Edge manual?


Look here:

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