GPRS 900/1800/1900 Triband
Convert GSM signal to PSTN line.
Perfect choice for PABX solution
Save cost by calling from GSM to GSM

GSMTONE operation:
Attach antenna
Insert SIM card
Connect telephoneConnect power - 9VDC @ 1500ma
Power on, a red LED should flash for a few seconds then go off.  
The LED should go on when off hook.
The network LED (bi-color) should flash when the GSM module is registered with the system.

Outgoing call:
Go off hook, Dialtone will appear.  
Enter the number; after a 5 second pause in entering numbers, the number will be dialed.
Go on hook when the call is complete.

Incoming call:
Dial the SIM card number; the telephone attached to the GSMTONE unit should ring.
Go off hook to answer.
Go on hook when the call is complete.

Security:
If GSM signal drop to certain level, the loop current will be off.
Loop current will be restore after GSM signal back to normal.