A system or method for communicating data over a voice channel between a transmitter and a receiver. In one embodiment, the system includes: (1) a silence detector, coupled to the transmitter, that identifies a pause in voice traffic that is to be transmitted over the voice channel and generates an interjection signal during the pause and (2) a data injector, coupled to the silence detector, that receives the interjection signal and responds by causing the transmitter to transmit data to the receiver over the voice channel.