| 摘要 |
A programmable thermostat 10 for controlling the actuation of, for example, a central heating system, in dependence upon temperature, is battery powered so that there is no need to connect the thermostat to a mains supply. The control of the central heating system is by way of a switching circuit 22 which has a first position in which the central heating system is energised and a second position in which the system is deenergised. The thermostat 10 has a processor unit 12 which monitors the level of the batteries powering it. If the power level remains below a preset value for a preset period of time a warning signal is generated. If the user takes no action in response to the warning signal, the thermostat 10 switches off the central heating system before the batteries become too drained to perform the switching operation. <IMAGE> |
