Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request From: Daniel Karrenberg Newsgroups: comp.dcom.telecom Subject: Re: Billing and Answer Supervision Message-ID: <5416@accuvax.nwu.edu> Date: 20 Mar 90 11:17:53 GMT Sender: news@accuvax.nwu.edu Organization: European Unix systems User Group Lines: 34 Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 10, Issue 189, Message 3 of 10 tell@oscar.cs.unc.edu (Stephen Tell) writes: >How can such a device work on a system where the PTT's counter runs at >different rates depending on distance, time of day, and so on? In the systems based on message units the local exchange (sometimes the toll exchange but never mind the details) will figure out to which charge band you are calling. As soon as call supervision indicates the call is completed it will send 16kHz pulses down the subscriber line. The pulses are spaced according to the tariff applying to the call. The pulses will reach a meter at the local exchange associated with your line. These meters (at least in Germany) mostly still are mechanical counters arranged in blocks of (I think) 25x25 which are photographed once a month. The photographs are used to key the meter counts into the billing system manually (believe it or not). Call supervision works on all national and most international calls. Some areas of the UK are a notable exception. In these cases you get billed for the ringing and there is nothing you can do about it. If you want a meter at home, the PTT whill remove the lowpass filter that blocks the 16kHz pulses and -voila- your meter starts ticking. Last time I saw them they were mechanical counters attached to a simple LC filter circuit. I am now living in the Netherlands and here they sell you counters with LCD displays. You can strap the unit price with jumpers and read them off in real $$s. Before anyone asks: Yes there is plenty of room for inflation in the design. :-) Daniel Karrenberg Future Net: CWI, Amsterdam Oldie Net: mcsun!dfk The Netherlands Because It's There Net: DFK@MCVAX