This unit is a small computer controlled portable Signal Sender for field or central office use. Its purpose is to provide DTMF, MF and Dial Pulse Signaling on the following circuit types: 2 wire loop, 4 wire loop, 4wire SF, 4 wire E&M, 2 wire E&M. Supervision on these circuit types may be long, SF or E&M. A reverse battery indicator is provided for loop type singaling employing reverse battery wink.

The T303B features self-contained operation, powered by a rechargeable battery pack, making it ideal for field operations. The internal monitor speaker and headset-jacks allow voice communications over the circuit being tested.