Which statement best describes CID (Caller ID) in alarm communications?

• A. It uses pulse dialing and cannot carry information strings.
• B. CID uses tone dialing, supports up to 16 digits, and can send zone and information strings.
• C. It transmits a continuous tone with no digits.
• D. It is slower than SIA and sends fewer digits.

Answer: (B)

CID in alarm communications is a data transmission method that uses the telephone line to send event information as digits and descriptive strings. It relies on tone dialing (DTMF) to transmit the digits, not pulse dialing, so data is sent as tones. The format supports a sequence of digits—up to about 16 in standard CID transmissions—and can include a zone identifier along with an information string describing the event. This combination lets the monitoring center know exactly which zone tripped and what occurred. It isn’t just a continuous tone with no digits, and while SIA is another reporting standard, CID’s defining features are tone-dialed digits up to 16 plus zone and information strings, which is why this statement is the best fit.