Abstract: 8 kHz ASK signals are produced by an electronic business set instrument to function as control or feature signals. To avoid the problems of transmitting the 8 kHz ASK over voiceband telephone lines over long distance, the least significant bit (LSB) of each 8 bit word representative of voice signals is caused to be at a predetermined level (e.g., low) when an ASK signal is present and at the other level (e.g., high) when there is no ASK. At the receiving end, the state of the bit is used to regenerate the 8 kHz. Detection of the ASK is performed by a high-pass filter.