| 摘要 |
PCT No. PCT/GB95/02292 Sec. 371 Date May 30, 1996 Sec. 102(e) Date May 30, 1996 PCT Filed Sep. 27, 1995 PCT Pub. No. WO96/10860 PCT Pub. Date Apr. 11, 1996A remote electricity metering system utilizes a central station (LC) to communicate with meters (U1-U13) over the mains (10-14), with messages to remote meters being relayed by intermediate meters and the route of a message being determined by the central station. The present invention provides alarm signalling whereby the meters can communicate directly with the central station. Each meter can generate a respective combination of alarm frequencies, preferably sequentially and inside the frequency band used for normal messaging, and the local controller monitors the mains for those frequencies. An error detecting and/or correcting code can be used for the alarm frequency combinations. The central station polls the meter or meters sending the alarm. The meters are microprocessor based, with the normal message signals and the alarm frequencies being synthesized from a sequence of digital values by a D/A converter. |
