| 摘要 |
777,993. Automatic exchange systems. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. Feb. 21, 1956 [March 11, 1955], No. 7159/55. Class 40 (4). In an arrangement for pre-allotting common equipments such as registers, a closed hunting circuit comprising pairs of cold cathode tubes VRO, VSZ, one pair for each equipment, operates whenever an equipment is taken into use to ascertain the next idle one, which is then marked by the firing of the corresponding one of a set of mutually extinguishing tubes VC. Assuming that tube 1VC is conducting, positive potential from its cathode primes tube 1VD. When an equipment is required a positive-going pulse over common lead DL fires 1VD, and hence positive potential is applied to lead MB1 to seize the corresponding equipment and to prime tube 1VA. After a brief interval a negativegoing pulse received over common lead SAPL fires the primed tube 1VA to start the hunting operation. Busy equipments are marked by positive potential on the corresponding B leads and idle ones by positive potential on the corresponding F leads, so that one or other of each pair of tubes VRO, VSZ is primed. Tube 1VA passes on the negative-going pulse to the cathodes of 2VRO, 2VSZ, and if the equipment corresponding thereto is busy 2VRO fires and passes on the pulse to the next pair of tubes. This action continues until an idle equipment is reached, when the other tube of the pair, say NVSZ, fires and passes on the pulse to fire NVC, the previously conducting tube 1VC being extinguished. Tube NVD is primed in readiness for the next demand. The initial operation of the allotter is started by an auxiliary tube VS which is fired by a positive pulse over lead SL. The high-tension sources HT1, HT2 are disconnected momentarily after each pre-allotting operation to extinguish the relevant tubes, and they may also be disconnected to disable the allotter when all the equipments are busy. |
