Scheme for power conservation in fire alarm system
An arrangement for conserving the alarm-state power supplied to numbers of light emitting devices included in respective addressable terminal units of a fire alarm system or the like. The addressable terminal units are connected to a transmission line or loop; and a loop controller cyclically transm...
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Zusammenfassung: | An arrangement for conserving the alarm-state power supplied to numbers of light emitting devices included in respective addressable terminal units of a fire alarm system or the like. The addressable terminal units are connected to a transmission line or loop; and a loop controller cyclically transmits address signals to the terminal units (polling routine); the controller functions, responsive to received data from those units, to generate an alarm-state display command signal for causing illumination of the light emitting devices of terminal units that are in alarm. In the case where a terminal unit comprises a master transponder to which a group of non-addressable conventional "slave" detectors is connected, the loop controller is programmed to disconnect such slave detector from the loop or line when more than one of them is in alarm. However, in the event of a large number of terminal units at scattered locations being in alarm, a tell-tale signal from each unit is highly desirable. Accordingly, it is arranged that all of their light emitting devices will be capable of indicating an alarm state. To this end, a blinking mode of operation is selected, whereby limited groups of devices (except for one) are turned on in sequence, the "ON" times being the same for all off the devices, but the "OFF" times being varied in dependence on the total number of devices being supplied with power. Consequently, power ON is time-divided among the groups, so that the total power consumed by all groups is no greater than would be consumed by a single group. |
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