Thread: "Butt" 'phone
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Old 27th May 2019, 3:40 pm   #34
Graham G3ZVT
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Join Date: May 2010
Location: Greater Manchester, UK.
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Default Re: "Butt" 'phone

One feature that bit phones tend to have that is absent on ordinary phones is the ability to monitor the line for speech and other noises without applying a DC loop. A silent wire-tap in fact.

A couple of thoughts about withheld numbers.
The number is available throughout the calls transit in the network, it is accompanied by a flag that in effect says to the terminating telco, "Here is the callers presentation number, please don't pass it to your customer".

No doubt OFCOM and other national regulators mandate that telcos honour the withheld flag, but it's worth pointing out, until August last year when they were withdrawn, I had a contiguous block of ten UK geographic DDIs from a VoIP provider who did not honour the flag and passed the CLI regardless.

Less controversially, many people who, rather than prefixing every number with 141, have all calls "withheld", often don't know that they can release their number when calling friends & family by prefixing 1470 before the dialled number or including the prefix in stored numbers. Certainly works on Openreach's exchanges.
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