How is the Caller-ID information provided ?
As a 1200 baud, 7 data bits, 1 stop bit data stream usually transmitted following the first and before the second ring signal on the line. Note that this is not a standard Bell 212 or CCITT v22 data format so a standard modem will probably not be able to receive it. Further, the serial information exists as such only from the recipient’s switch to the callee’s location. Between carriers the signal exists as data packets. The signal is provided before the circuit is complete: picking up the receiver before the data stream is finished will stop/corrupt the transmission. Currently there are two types of information returned: a “short form” which contains the date/time (telco and not local) of the call and the calling number or error message. The “long form” will also contain the name and possibly the address (directory information) of the calling phone. The “short form” stream consists of a set of null values, followed by a two byte prefix, followed by the DATE (Month/Day), TIME (24 hour
