Contact ID Protocols for Alarm System

Contact ID protocol is used in alarm systems where there are several alarm monitors. The protocol allows the information to be entered at any of the monitors and it is fed back to the central alarm station. The operator at the central station can identify where the information came from according to the protocol. Contact ID alarm is designed to minimize the amount of time needed to transfer information from the system to the central controller while reducing the transmission error rate. Contact ID alarm is mostly used in community and the central alarm station can receive the alert directly.

1. Handshake Tones
The handshake tone is sent to the transmitter from the receiver. This tone is used to signal that the communication channel is open and that transmissions can be sent. The protocol requires that 2 to 5 seconds are allowed to pass for the phone line to be settled before the transmission occurs, so the information will be transmitted without interference or the risk of dropped calls.
2. Message Blocks
Transmissions can be sent in a block. Message blocks allow several messages to be combined together and sent over the connection at the same time. These types of transmissions are for standard reporting information that doesn't require immediate action, such as status reports of the system. Each message block reports on events that have occurred in the system and reports when they occurred. Message blocks are not used to report contact ID alarms, as alarm transmissions require immediate attention.
3. Composition
Messages are created with a specific composition so that they can be easily identified as the messages come in to the central control station. The composition of the message is in the following order: the account number, the message type, the event qualifier, event code, the group number and the zone number. Each of the composition elements of the message are designed to help to quickly move messages into the proper priority.
4. Kissoff Tone
Once a message has been received the contact ID alarm will send a kissoff tone back to the transmitter. This tone tells the transmitter that the message has been received successfully. The tone is sent at a frequency of 1,400 hertz and is sent by the receiver for a maximum of one second to the transmitter. The transmitter will register the kissoff tone as being valid after it has received a constant tone for 400 milliseconds.