17 Dec
2003
17 Dec
'03
11:17 p.m.
Tim May wrote:
(Even the _ability_ to block a pay phone, qua pay phone, must imply that pay phones send out some kind of signal announcing themselves as pay phones, which I had not heard of before. I assumed a pay phone was Just Another Phone Number.)
Telephone switches generate (receive) a digit that is known as Call Type. Simplistically, Call Types may be 1+ for regular calls, 800 for 800 calls, Conference, and 0+ for operator/payphone call. One of the switch features may be some kind of call type blocking, or passing the call type to the termination side, such as the pager company computer. - Igor.