Simultaneous transmission of voice and data over the voice channel of a digital wireless communications network, such as a “cell phone” network, is reconfigurable on the fly among multiple operating modes, including a lull detection mode in which data is transferred during a lull or quiet period in the voice content. Additionally, control signaling in the voice channel, rather than over a separate control or “overhead” channel is employed to support SVD. The described system operates transparently over any wireless telecommunications system.