Exp dtmf n advantages of dtmf over pulse dail mech Draw n explain caller id What do u mean by cross talk n exp diff types of cross talk What do u mean by side tone and its importance Exp pagging system in detail Draw n exp functional block diagram of telephone set Dual-tone multi-frequency signaling (DTMF) is used for telecommunication signaling over analog telephone lines in the voice-frequency band between telephone handsets and other communications devices and the switching center. The version of
DTMF that is used in push-button telephones for tone dialing is known as Touch- Tone, was first used by AT&T in commerce as a registered trademark, and is standardized by ITU-T Recommendation Q. 23. It is also known in the UK as MF4. Other multi-frequency systems are used for internal signaling within the telephone network.
Dial ulsing originated with a rotary dial integrated into telephone instruments, for the purpose of signaling. Subsequent applications use electromechanical or electronic circuits to generate dial pulses. The pulses are generated through the making and breaking of the telephone connection (akin to flicking a light switch on and ofO; the audible clicks are a side effect of this. As a result, all that is really needed to dial a number with pulse dialing is a switch. Each digit in the number is represented by a