Improvements in and relating to reciprocating mechanisms

958,663. Switches held set and freed mechanically; keyboard switches; electrically-released switches; electromagnetic switches. TELEPHONE MANUFACTURING CO. Ltd. July 4, 1961 [July 6, 1960 (2)], Nos. 23558/60 and 23559/60. Heading H2B. An operating member, e.g. the push-button of a switch, is latchable in one position, the latch comprising a relatively movable pin and closed track, there being provided in addition a second track which is alternatively engageable by the pin so that " push-push " and " push-tolock " operation are obtainable as alternatives. One track is shown in Fig. 2 (23558/60), the pin 6 being so mounted as to be urged down on to the track and to the left. The step 10 thus prevents the pin from moving into the left-hand leg 9 of the track when moved upwards from the position shown. The track may be carried by the push-button and the pin by the fixed part of the switch, or vice versa, and in the first case the track may be used as a cam to actuate the switch contacts. An indicator lamp may be mounted on the fixed part and within the push-button which has a transparent cap. Several push-buttons may be arranged in a group and interlocked by a bar 13 so that operation of any button releases a previouslyoperated button. The second track comprises a shoulder 15 on which the pin 6 rests in the depressed position, Fig. 4 (23559/60), not shown, lateral movement of the bar 13 by the pin of another button moving the pin 6 from shoulder 15 through a passage 12 to release the depressed button. In a modification, Fig. 1 (23559/60), not shown, the second track is formed separately from the first track and the pin is selectively positioned to co-operate with the desired track depending on whether the button is to be used in a group or singly, respectively. The button may be operated by a pulsed electromagnet. Specification 958,664 is referred to.