SIM Cards and Modem
As with a cell (mobile) telephone, the SIM card is the small card that allows connection with a mobile telephone network.
The modem is an integral part of the Control Board.
The SIM card is inserted into the card holder on the telephone modem on the Control Board. The SIM card may be a roaming SIM and be able to pick up the signal of the strongest mobile phone signal available, or it may be a national SIM card issued by a company locally.