The easiest way to try out the TC35 is to connect it via a Serial to USB connector lead. These leads can be obtained from eBay for about £1.50 in August 2014.
A power supply is needed, I used a 5 volt 1.0 amp supply and although a 2 amp supply is recommended this only seems to be needed when transmitting voice. You will need a terminal program like RealTerm or Putty, both are free to download, but I prefer RealTerm.
You need to determine the Com port being used, so plug the USB to Serial lead into the PC and open up the Windows Control Panel. Click on the System / Hardware / Device Manager Tab and look for the Ports, (Com and LPT) make a note of the port used by the USB to Serial lead. Mine showed USB – SERIAL CH340 (Com7). Later versions of Windows , from Windows 7, should find the driver automatically. Earlier versions will need a driver which you can normally find on the Internet, I just searched for ‘driver for CH340’.
Now open up the terminal program, enter the port and speed details (9600 for the TC35). Make sure a SIM card has been inserted and connect the Serial to USB connector. Apply power to the TC35, the top left LED will light. Press the button and the top right LED should light up, flashing ON for 600 ms then OFF for 600 ms. This shows the unit is activated, but not connected to a Network. If the flash rate changes to a brief flash, followed by a long pause it shows the unit has connected to a Network. My unit has never connected automatically and I always manually connect it.
In your terminal program type AT followed by ENTER, the unit should respond with OK if not check the connections and that the correct port and speed have been entered. Type AT+COPS=? And the available networks will be listed. The five digit code is made up of 234 for the UK and 33 for Orange, 15 for Vodaphone and 10 for O2. To manually connect to your service type:
AT+COPS=1,2,23433 for Orange, or AT+COPS=1,2,23415 for Vodaphone. Note you can only connect to the network supported by your SIM, although an EE card will connect to Orange, One2One and TMobile.
To confirm you are connected the LED will flash briefly with a long pause. Type AT+CREG? And the response should be 0,5 to show the network was connected manually.
Once you have confirmed that the unit is working correctly you can move on to controlling it with an Arduino.