pins on a vertical axis. This style of plug/socket was used by university laboratories (from batteries) and the BBC, and is still in use on parts of the London Underground for 110VAC voltage supply. In the 1960s they were used for 240VDC in the Power laboratory of the Electrical Engineering department of what was then University College, Cardiff. Power was supplied by the public 240VDC mains which remained available in addition to the 240VAC mains until circa 1969, and thereafter from in-house rectifiers. They were also used in the Ministry of Defence Main Building on circuits powered from the standby generators to stop staff from plugging in unauthorised devices. They were also known to be used in some British Rail offices for the same reason. Italian BTicino brand Magic security connector The Italian manufacturer BTicino in the 1960s introduced an alternative to the Europlug or CEI 23-16 connectors then in use. The socket is rectangular, with lateral key pins and indentations to maintain polarisation, and to prevent insertion of a plug with different current ratings. Three single-phase general purpose connectors were rated 10 A, 16 A and 20 A; and a three-phase industrial connector rated 10 A; all of them have different key-pin positioning so plugs and sockets cannot be mismatched. The socket is closed by a safety lid (bearing the word ‘'Magic'’ on it) which can be opened only with an even pressure on its surface, thus preventing the insertion of objects (except the plug itself) inside the socket. The contacts are positioned on both sides of the plug; the plug is energised only when it is inserted fully into the socket. The system is not compatible with Italian CEI plugs, nor with Europlugs. Appliances were never sold fitted with these security plugs, and the use of adaptors would defeat the safety features, so the supplied plugs had to be cut off and replaced with the security connector. Even so, the Magic security system had some success at first because its enhanced safety features appealed to customers; standard connectors of the day were considered not safe enough. The decline of the system occurred when safety lids similar to the Magic type were developed for standard sockets. In Italy, the system was never definitively abandoned. Though very rarely seen today, it is still marked as available in BTicino’s catalogue, (except for the three-phase version, which stopped being produced in July