dbb@aicchi.chi.aic.com (Ben Burch) (01/18/91)
In the US (and I imagine that the UK is similar since we can exchange hardware) many (not all) COs return a "disconnect pulse" when a call terminates. The width of this pulse varies from 100 ms to 500 ms depending on the type of switch you are connected to. The pulse is simply a loss of loop current. You can often tell if this happens with a lighted dial phone. If the light blinks after a caller hangs up, then you get the pulses. In the hardware I've worked on, we use an opto and a couple of diodes to detect both ringing and loop current. Ben Burch dbb@aicchi.chi.aic.com
ruck@reef.cis.ufl.edu (John Ruckstuhl) (01/21/91)
In article <16083@accuvax.nwu.edu> abm88@ecs.soton.ac.uk (Morley A.B.) writes: >Does anyone know how I go about detecting the end of an *incoming* >call on an ordinary residential line? I thought I once read that >the voltage changes or someting. I am in the UK. My answering machine (a Sony ITA-500) cannot reliably detect the end of an incoming call on an ordinary residential line. My previous answering machine (a PhoneMate) had the same problem, and I always blamed the machine until I saw the problem on the new answering machine. The problem causes great confusion, sometimes leaving the machine in an error state which might cause lost messages :( A Southern Bell serviceman visited, and said my line was as clean as they get! I explained my problem, but he couldn't help me. BTW, I did my simple inside wiring -- 30' of two pair from the inside block dead-ending at the jack for the answering machine, and another 20' of 2pr from the inside block to a dead-end with a jack. What should be my next step? (Also, has anyone converted a Sony ITA-500 to an ITA-600? The 600 is a "speaker-phone"; the 500 just has "on-hook dialing") Thank you for your help. Best Regards, John R Ruckstuhl, Jr University of Florida ruck@cis.ufl.edu, uflorida!ruck