Circuit For Improving Noise Immunity In Tone Detection
Original Publication Date: 1980-Feb-01
Included in the Prior Art Database: 2005-Feb-13
The noise immunity circuit NG is used in connection with a tone detector TD which makes the discrimination between a modem signal and a signaling tone transmitted for alarm purposes on the same line as the modem signal, the signaling tone having a frequency outside the frequency band of the modem signal. The function of the circuit is to prevent pulsed noise the line from being decoded as a signaling tone when there is no modem signal.