Tone Detection in a Multipoint Transmission Network
Original Publication Date: 1985-Oct-01
Included in the Prior Art Database: 2005-Feb-19
A remote baseband modem T2 is made to generate and send a tone frequency (e.g., 225 Hz) to signal a predetermined event (e.g., power going off) to a control modem (CTRL). Such a tone may be transmitted at any moment, for instance, while a local modem T1 is sending data. The tone/data ratio at the CTRL receiver input may be rather low. The frequency bandwidth of base band modems already includes 225 Hz. Therefore, either the CTRL receiver will not detect the tone generated by the remote modem T2, or it might detect a false tone due to data. The latter case is to be avoided, since the system is made to drive the CTRL unit to interrupt any traffic upon detecting a tone.