| 摘要 |
<p>An apparatus for selectively switching a mode of operation of a detector between a source mode, where the detector supplies an electric current representative of the signal, and a sink mode, where the detector draws an electric current representative of the signal. The apparatus comprises a detector 20 configured for connection to a signalling terminal 29, switching means 24, e.g. a timer and latch system, for configuring the detector 20 to operate in one of sink mode or source mode and a voltage comparator 26. The apparatus 20 is configured to selectively switch to operate in sink mode or source mode based on a comparison of a voltage from the signalling terminal 29 received at the voltage comparator 26 with a threshold voltage. The apparatus can be a gas detector, and can be connected to an alarm system. The apparatus can further comprise memory and a processor.</p> |
