Prepayment systems.
A prepayment system for controlling the supply of electricity, gas or water to a consumer comprises a metering or timing unit having a receptacle for receiving a prepayment token in the form of a key having a memory containing credit data. The metering or timing unit permits the supply of the commodity until the credit represented by the credit data in the key memory is exhausted. The system is provided with a push-button operated emergency supply facility, which permits the supply to continue for a predetermined time, typically four or five days, after the credit is exhausted. <IMAGE>