Patent GB-298932-A (GB)
Title: Improvements in or relating to telephone systems
IPC: H04M15/10
Filed: 1927-07-16
Abstract: 298,932. Automatic Telephone Manufacturing Co., Ltd., and Ostline, J. E. July 16, 1927. Automatic exchange systems. - In a testing equipment for meters, impulses are sent to the meter under test which, if it responds properly, sends back impulses to prevent the giving of an alarm. The equipment is primarily applicable for meters which, on operating, complete locking circuits for themselves as described in Specification 261,880, but the circuits of the equipment may be changed by a key so that meters which are not self-locking may be tested. In the arrangement described, ten impulses are sent to the meter over a resistance, followed by ten further impulses over an increased resistance, a signal being given on failure of the meter to respond and a different signal if the test is completed satisfactorily. The provision of metering impulses of two strengths enables a meter to be adjusted so that it will not operate with reduced impulses. The equipment is wired up to sevenpoint plug, battery being applied over 12 and intermittent ground over 7. Resistances are connected between 2, 3 and 3, 4, and the meter is connected between 5, 6. Relay E operates over 2, resistance 3, 31, 8, meter 19, 15 to ground at 34, locks itself up and completes the circuit of D. The meter does not operate at the time. Relay C, which is intermittently operated over 13. 7 sends impulses over 14 to the magnet 23 to step wipers 25, 26, and at 16 connect intermittent ground to terminal 6 of the meter. If the meter responds, it connects further ground to 6 so that the next relapse of C completes a circuit for A over 16,. 19, 6. Relay A locks a self over 9, 17, 20 to ground at key LK breaks the meter circuit at 8, and at 10 opens a point in the locking circuit of two-step relay F. The next energization of C unlocks A and these relays continue to interact until ten impulses are sent to the meter and the wipers 25, 26 are stepped on the tenth terminals. when H energizes over 26, and at 31 removes the short circuit across 3, 4 to throw a further resistance into the meter circuit. A second series of impulses are then sent to the meter and magnet, and relay B energizes over 11, 26, opens the circuit of C at 13 to stop the impulses, and replaces holding ground at 34 for E by ground at LK over 20. 17, 9, 16, 19, meter 8, 34. Relay B also connects intermittent ground from 7 to relay 33 over self-interrupting contacts 35 to operate a bell or otherwise to signal the completion of the test. On removal of the plug, E falls back followed by D, A, B, H and the homing circuit for magnet 23 is completed. If at any stage, the meter fails to respond, it will not return ground over 6 to operate A, and relay F will then energize over 27, 17, 20, LK, and lock itself over 28, 10. Relay G now operates over 27, 17, 20, LK to connect permanent ground from 30 to relay 33 to signal that the meter is faulty. The attendant may release 33 by operation of key RK. To test meters which are not selflocking and do not return ground over 6 to operate relay A, attendant throws key LK. Twenty impulses are then sent to the meter, and magnet and relay B operates over right-hand springs of LK and wiper 26 to connect intermittent ground from 7 to relay 33 to indicate completion of test as before. In this case it is necessary to read the meter before and after the test to discover if it is faulty.