brian@uunet.uu.net> (04/30/91)
In article <telecom11.310.7@eecs.nwu.edu> wmartin@stl-06sima.army.mil (Will Martin) writes: > As a practical matter, if a telco implements Caller-ID services, is it > going to send the data down the line on each and every call to each > and every instrument or line, or is it going to limit the data > transmission so that it only goes to people who have paid for it? > Would it be cheaper to send it to everyone or to do an edit and send > it only to the limited subset? As far as I know, it actually takes some additional equipment to implement the service. Unlike TouchTone, where the dial registers were simply augmented with DTMF decoders, there is actually special tone generating equipment switched into the call when caller ID is used. In the Bellcore specs TR-TSY-000030 and TR-TSY-000031 (which describe the service and it's physical layer interface) there are words stating "Less than .01 of Average Busy Season Busy Hour (ABSBH) attempts to allocate SPCS transmission equipment for this service should see all circuits busy." (SPCS == Stored Program Control System) BTW: The reason for the ANI coming in between the first and second ringing cycles is that the ringing voltage from the first ring cycle is used to wake up battery powered terminal equipment. brian