Improvements in or relating to selective calling systems

... 1,116,912. Testing radio calling equipment. MARCONI CO. Ltd. 26 July, 1966 [21 Oct., 1965], No. 44558/65. Heading H4L. In a selective calling arrangement of the type in which a plurality of resonant devices at a receiver are selectively responsive to predetermined frequencies within a predetermined range of frequencies, a warning being given when all the devices have responded, testing means are provided at the receiver for applying to the devices oscillations which are swept over said frequency range and for actuating the warning means when all devices have responded. Calling system.-As shown, when a receiver R receives the appropriate calling tone combination for the receiver, e.g. one pair of tones transmitted for 1 second followed after a pause of “ second by a second pair of tones, resonant reeds A5, A6 vibrate, followed by reeds A7, A8, causing charges to be built up in associated integrating circuits A9 to A12. These integrating circuits are connected via normally non-conducting ...