... GSM cellular network incoming.3,DTMF Caller ID.4,Support secondary dial.5,Lock card, lock terminal.6,Send polarity reversal signal for ... while connection.7,Sending 12/16KHz pulse for billing meter while connection is also compatible.8,Support GPRS . (Optional)9,Rechargeable ... 5Vadapter AC 110~240 input7,DTMF Receive: > -23dB insure receiving.8,DTMF Receive sensitivity: 99.99%9,Insertion loss: ≤0.5dB