BS 8521:2009 pdf download

BS 8521:2009 pdf download.Specification for dual-tonemulti-frequency (DTMF) signalling protocol for social alarm systems.
6.4 Clear down ([AID)
On receipt of the “clear down” command, the local unit and controller shall respond by sending the acknowledge tone and disconnect from the telephone line.
NOTE It is advisable for grouped equipment that a “clear” command precedes a “clear down” command so the presence of outstanding calls is indicated, otherwise a complete new communications session will need to be established to service outstanding alarms.
6.5 Null command (keep alive) ([A] #)
NOTE This command serves as a “keep alive” indicating that the channel with the ARC is still active.
When contact between an ARC and local unit and controller is established and no control activity is taking place, a “null” command shall be sent from the ARC to the local unit and controller at intervals of not more than 1 mm, commencing from receipt of the acknowledge tone associated with the previous command sent by the ARC.
If no acknowledge tone is received by the ARC within (600 ± 30) ms of cessation of the “null” command, the ARC shall repeat the command to a maximum of four attempts.
If either the local unit and controller or the ARC fails to detect the “null” command or acknowledge tone after an elapsed time of 130 s, it shall clear down and disconnect from the telephone line.
6.6 Selection of a local unit in grouped equipment
NOTE The fields in each string are defined in 5.2.
The local unit selection command sent by the ARC to the local unit and controller shall be in the following format:
AORRRR#
The local unit and controller shall respond to the local unit selection command by sending a data sequence representing the status of the local unit and any pending alarm event as appropriate. This data sequence shall be in the following format:
ARRRR EEE LLPSS
6.7 Request for information on outstanding calls NOTE The fields in each string are defined in 5.2.
The command sent by the ARC to the local unit and controller requesting details of pending calls shall be in the following format:
Al NNNN#
If NNNN = 0000, then details of the next highest priority call at the local unit and controller shall be sent. If NNNN = 9999, then details of all pending calls shall be sent.
Upon receipt of the “outstanding call request” command, the local unit and controller shall respond by sending a data sequence representing the status of each alarm event as appropriate. This data sequence shall be in the format:
7 Programming
7.1 General
The command for entry into the programming mode shall be in the following format:
ACFFFF#
where:
A and # are the message string start and stop delimiters; C is the “enter programming” command (see Table 1); FFFF is a four-digit security code, to prevent unauthorized access to the programming facility of the local unit and controller.
The default security code for all equipment shall be a null field (0000), unless or until such time as a specific security code is assigned to a particular piece of equipment in place of the default.
If the security code is accepted, the local unit and controller shall respond with an acknowledge tone and the equipment shall be placed in programming mode.
If the command is rejected, either because the security code is incorrect, the remote programming is not supported, or the local unit and controller is not in programming mode, the local unit and controller shall respond with a data response in the format A 0000 #. This shall be acknowledged in turn with an acknowledge tone by the ARC.
The command for exit from the programming mode shall be in the following format:
A2TTNN#
where:
TT is the system type assignment (see Table 3);
NN = 32 (see Table 10).
The local unit and controller shall respond by returning the data sequence in the following format:
AUNN #
where:
TT is the system type assignment (see Table 3);
NN = 32 (see Table 10).
NOTE An example of programming is shown diagrammatically in Figure 3.