Same in the UK. Ring voltage is a low frequency bipolar spike waveform of a
100V or so amplitude, Originally designed to hit the bells firmly, the
waveform seems to have been kept for legacy reasons. Modern phones rectify
the AC ringing voltage, after it has been separated by a capacitor from the
DC line voltage of 50V, and use this to supply the audio ringer. Ring
tones are generated locally in response to the network signalling
instructions and returned to the caller.
Andy G4JNT
-----Original Message-----
From: [email protected] [mailto:[email protected]]
Sent: 2001-11-08 06:51
To: [email protected]
Subject: Re: LF: Re: Ringing Voltage on Telephone, boo-boo
I don't know how it is in Canada, but in the States, the 20Hz
component is
the only ringing voltage sent across the line to the
telephone set, which can
readily be confirmed by sticking a blocking capacitor and a bridging
transformer acorss the line and looking at the result directly on an
oscilloscope. The modulated audio frequency tones are sent from the
switching office back to the caller, not to the recipient.
Locally, the ringing voltage is 90V RMS, riding on the normal
on-hook DC of
about 50 volts.
73,
John
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