Typically, solid-state oscillators have replaced them. In smaller offices, special sub-cycle magnetic oscillators were used. Large central offices used motor-driven generator sets for both ringing and other signals such as dial tone and busy signals. Ringing voltage is produced by various sources. Some non- Bell Company system party lines in the US used multiple frequencies for selective ringing. In Europe it is around 60–90 VAC with a frequency of 25 Hz. 90 volts AC with a frequency of 20 hertz. The ringing signal in North America is normally specified at ca. (SLC is a trademark of Alcatel-Lucent, but is often used generically.) Telephones with electromagnetic ringers are still in widespread use. This is done at the Central Office, or a neighborhood multiplexer called an "SLC" for Subscriber Line Carrier. On a POTS interface, this signal is created by superimposing ringing voltage atop the −48 VDC already on the line. For mobile phones, the network sends a message to the recipient's device, which may activate a sound, or a visual or vibrating indication. The ringing current originally operated an electric bell. Landline telephones typically receive an electric alternating current signal, called power ringing or ringing signal, generated by the telephone exchange to which the telephone is connected. Customers can buy or generate custom ringtones for installation on the device.Ī telephone rings when the telephone network indicates an incoming call, so that the recipient is alerted of the call attempt. Originally referring to and made by the electromechanical striking of bells, the term now refers to any sound on any device alerting of a new incoming call-up to and including recordings of original telephone bells.Įlectronic telephones, especially smartphones, are manufactured with a preloaded selection of ringtones. Electromechanical ringer in a 20th century landline telephoneĪ ringtone, ring tone or ring is the sound made by a telephone to indicate an incoming call.
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