on a standard BT set up, which terminal operates the ringer on a phone?
telephone terminals
- Thread starter sparkiedave
- Start date
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A
Alarm
On a standard there is no seperate ringer.
2 & 5 are the line, or A & B.
3 used to be the ringer.
http://www.rob-r.co.uk/other/UKphonecatwiring.htm
The above does show the older methods.
2 & 5 are the line, or A & B.
3 used to be the ringer.
http://www.rob-r.co.uk/other/UKphonecatwiring.htm
The above does show the older methods.
P
Paul_C
On a standard what?
The majority of phones manufactured today use only a two-wire connection and don't require a separate ringer feed, but there are good many older phones in use which will not ring without the full three-wire connection. The whole range of BT Statesman, Ambassador, Viscount, etc. come to mind.
A
Alarm
Standard 2 wire, and older will need the 3rd wire hence the link to show how and why.
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The system was designed to have one bell capacitor of known value in the master socket and to feed the bell signal via terminal 3 to all phones. A test resistor in the master socket enables line testing to give accurate results about the quality of the line from exchange to master socket.
Phones with only 2 wires have a bell capacitor built in to the phone. This adds to the amount of capacity across the line and complicates if not prevents reliable and accurate testing of the line from the exchange. This is the reason why the subscriber ( customer ) is often asked to disconnect phones during line testing.
Ironically micro filters have had to have bell capacitors fitted in them and thus they convert a three wire phone ( as the system was designed ) to be two wire in order to be "compatible" with ADSL requirements.
Phones with only 2 wires have a bell capacitor built in to the phone. This adds to the amount of capacity across the line and complicates if not prevents reliable and accurate testing of the line from the exchange. This is the reason why the subscriber ( customer ) is often asked to disconnect phones during line testing.
Ironically micro filters have had to have bell capacitors fitted in them and thus they convert a three wire phone ( as the system was designed ) to be two wire in order to be "compatible" with ADSL requirements.
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