Abstract: A communication apparatus (1) for communicating over an electrical power cable (3). The communication apparatus (1) comprises a transmitter circuit (5) adapted to transmit a communication signal; and a receiver circuit (6) adapted to receive a communication signal from another communication apparatus (1). The communication apparatus (1) is adapted to transmit and receive communication signals over the power cable (3) both when said power cable (3) is conducting electricity and when said power cable (3) is not conducting electricity.
Abstract: A communication apparatus (1) for communicating over an electrical power cable (3). The communication apparatus (1) comprises a transmitter circuit (5) adapted to transmit a communication signal; and a receiver circuit (6) adapted to receive a communication signal from another communication apparatus (1). The communication apparatus (1) is adapted to transmit and receive communication signals over the power cable (3) both when said power cable (3) is conducting electricity and when said power cable (3) is not conducting electricity.
Abstract: A smoke detector unit (20) comprising a housing containing a smoke detector (24) and at least two component mounting boards, such as printed circuit boards, in a stacked arrangement, the housing having at least one air gap (34), wherein one of the boards (36) is inverted with respect to the other and the detector is positioned on the lower board whereby, in use, the detector extends upwardly between the boards. The housing may be in the form of a ceiling rose.