GSM interface that simulates a PSTN line. If connected to a telephone device (analogue PABX, analogue phone etc.), it allows to make and receive phone calls through GSM network (not suitable for FSK signallings, as modem and/or FAX).
It can be used in the security systems to connect phone dialers and/or control panels with PSTN dialer.
Advanced GSM functions: continuous credit check on the SIM card (if pre-paid) with SMS signalling low credit to a programmed number, SIM card expiry check with SMS sending to a programmed number; automatic update of the SIM card expiry in case the residual credit is higher than the one previously stored (after a credit recharge).