Phone ring established

Phone ring is well established if there is an incoming call. The period starts from the fact that early telephones were ringing mechanism consisting of Bell and electromagnetically-driven hammer, producing a ringing sound. Aforementioned signal power electromagnet to move quickly and with the release of the hammer, find Bell. This "inductor" Bell System is still widely used. ringing signal sent to the customer on the phone is AC 90 V and 20 Hz in North America. Europe is at a frequency of about 60 -- 90 volts AC 25 Hz

While still produce sound, called "ring" rather than manufactured telephones electronically produce a warbling, Chirping or sound. Change the ring tone can be used to indicate characteristics of incoming calls (for example, rings with a shorter interval between them can be used to signal a call this number).

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