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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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11th Dec 2017, 10:01 pm | #21 |
Triode
Join Date: Nov 2016
Location: Frinton on Sea, Essex, UK.
Posts: 45
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Re: Phone accounts / bills
metering was normally done from the main exchange (GSC) using line reversals on the junction routes to the dependant exchanges, the local dependant would detect the line reversal and convert to a +50V pulse on the P wire to operate the subs meter. Subs private meter (SPM) used balenced 50Hx pulses on the A and b wire fed from the local exchange, the local exchange used the same charging information for the SPM and line reversal metering, and also the charge advice service (*411#) . when the billing system changed to "off switch charging" the accuracy was left in limbo so only the initial answer pulse could be used. Payphones ( electronic versions) used to use this to start charging but had there own charging system to workout the rate to be used.
the withdrawal of spm meters in 2008 was linked to the introduction of 21cn, this was never rolled out and only a few switches in south wales were changed over. |
11th Dec 2017, 10:08 pm | #22 |
Triode
Join Date: Nov 2016
Location: Frinton on Sea, Essex, UK.
Posts: 45
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Re: Phone accounts / bills
test lines had a cct comprising of a capacitor/resistor/diode in parallel in series with the B wire. the capacitor allowed the speech to pass the resistor provided a small dc feed but not sufficient to operate the relay in the exchange to signal the call had been answered and the diode was to allow the ringing to be tripped. worked well on strowger systems but not on the digital systems. the digital systems used markings against the called line too send a C7 message back to the calling site when the call was answered, the signal would be ANSwer for normal lines and answer no charge (ANC) to suppress billing at he orig exchange
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11th Dec 2017, 11:32 pm | #23 | |
Dekatron
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 9,642
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Re: Phone accounts / bills
Quote:
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12th Dec 2017, 2:04 am | #24 | |
Dekatron
Join Date: May 2010
Location: Greater Manchester, UK.
Posts: 18,713
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Re: Phone accounts / bills
Quote:
You have precisely described the circuit I "invented"* as a teenager, a small amp was required to push sufficient outgoing speech into the line via the dc blocking capacitor. * "Invented" by accident. The original project was a home made telephone answering machine, where the line seize relay did not reliably latch, and merely tripped the ringing.
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-- Graham. G3ZVT |
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