Q. Tone used in stronger telephony?
Dial Tone: This tone is used to specify that exchange is ready to accept dialled digits from subscriber. Subscriber must start dialling only after hearing the dialing tone. A number of times, though, a few seconds may elapse before the dial tone is heard. This occurs specifically in common control exchanges that use shared resources for user interfaces. Dial tone is a 33 Hz or 50 Hz or 400 Hzcontinuous tone as demonstrated in Figure. 400 Hz signal is generally modulated with 25 Hz or 50 Hz.