The SFA-4 industrial alarm

The SFA-4 Alarm system is a multiplexed system using the MEDCON A data transmission standard, a pulse width modulated signal, on 2 core inter-panel wiring, capable of displaying up to 60 alarm conditions. Each SFA-4 alarm displays four alarm conditions, with a normal lamp for each, using long-life 5 x 20 mm block LEDs..
Signals from plant or other monitored equipment are connected into the SFA-4. As an alarm condition occurs, the appropriate alarm condition will flash and the audible alarm will sound. Operating the Mute switch will silence the audible on that panel and convert the flashing lights to steady (the audible on any other panels is not affected). If the condition remains, the audible can be selected to re-trigger, requiring re-muting. In this case, if a condition is to be in an alarm condition for a prolonged period, e.g. for maintenance, the re-trigger can be prevented by silencing the audible with the Lockout button within the panel. The audible will not then sound for that condition of that service until it has returned to normal and then back to alarm condition. A volume control is fitted within the panel. A loud speaker is used for the audible rather than a buzzer, to give a mellow sound which, whilst drawing attention to the alarm condition, can be tolerated by staff otherwise occupied.
Operation of the test button on the front of the panel will cause the normal lamps to illuminate, the alarm conditions to flash and the audible to sound.
The alarm is housed in a steel enclosure with a plastic bezel. Within the enclosure are mounted the power supply with battery reserve, control board with lamps, selector switches etc. . The battery reserve enables the system to remain in operation for up to 4 hours .

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