Abstract: Telephone sets associated with terminal units such as modems or telecopiers generally need to be used without the handset being lifted off the gravity switch. Such telephone sets also tend to include electronic circuitry which is powered by DC derived from the telephone line via a diode bridge (11) to protect against reversals of line polarity. The line is initially looped by a user-operated switch (T) having contacts (t1) connected in parallel with the gravity switch looping contacts (cc1), and thus on the line or AC side of the bridge (11). Once adequate power is supplied to a controlling microprocessor (5), it causes a relay (RE) to close line-holding contacts (re1) in parallel with the looping contacts already mentioned (t1, cc1). The loop is released by means of a release transistor (15) connected in a common return wire on the DC side of the bridge (11).