Patent GB-749669-A (GB)
Title: Apparatus for testing multi-conductor cables
IPC: G01R31/50
Filed: 1954-11-19
Abstract: 749,669. Electric tests. LINK AVIATION, Inc. Nov. 19, 1954 [Feb. 18, 1954], No. 33603/54. Class 37. In apparatus for identifying conductors and testing continuity of conductors the latter are connected between a master unit and a remote unit and a selective switching device in the master unit establishes a circuit through one of the conductors to operate corresponding indicating means in both the master and remote unit. In the embodiment shown, Fig. 2, the test cable 20 is plugged into remote and master units 15, 17 and selector switch S-1 rotates to light indicator lamps 1-A, 2-B, 3-C, &c. corresponding to cable cores 1-A, 2-B, 3-C, &c. The indicator lamps for the two units are arranged as at 12 in Fig. 1 (the latter in fact represents the master unit 15) with patterned or numbered sockets 14 to receive corresponding cable plugs. Testing 5-core cable.-Switch S-2 is closed so that induction motor M-1 drives cam contact 56 to feed pulses to control coil 50 and step selector switch S-1. The latter scans clockwise and when contact arm 49 reaches contact 65 and if core 1-A links lamps 1-A the latter are illuminated and relay K-1 operates to stop the motor M-1. The operator then momentarily depresses switch S-3 at intervals to open circuit coil 50 and step S-1 to next contact 66 and so on and for each step watches for illumination of the correct lamps, 2B for core 2B and so on, until all 5 cores are tested. When core 5E has been tested depression of S3 causes arm 49 to rapidly reach home contact 44 and light up home lamp 39 and energize relay K-1 to stop motor M-1. If during the tests the contact arm 49 sweeps past a contact the corresponding lamps do not light up and relay K-1 remains de-energized and this condition corresponds to open circuit or incorrect connections to cable plug pins. The rheostat R-2 is provided for adjusting the current at which relay K-1 cuts-in so that only open circuits above an allowable resistance will be indicated. Also if two or more cores are connected together this is indicated by the dim illumination of lamps 1-A &c. (parallel connected by the short circuit) in the remote unit 17. Cross-connections in the plugs (e.g. core 1A to plug pins 1A and 4D) are checked by the lighting up of the appropriate lamps in the remote unit 17 (e.g. lamps 1A and 4D). Miscellaneous details.-If spare cores are provided in the cable 20 (e.g. as at 71) the control switch S-4 is changed to lower position and one end of the spare core is connected to plug pin 1-A (or other pin) and the loose end 71 is dipped into mercury pool 72 or 721 to light lamp 1-A and lamp 75 or 74. A resistor R-1 is provided in the spare check circuit so that the lamps are as fully illuminated as when the fully connected cores are tested. The control switch S-4 may be provided with an extra set of contacts to stop running of motor M-1 during spare core testing. For bench work one operator observes both units; for installed cables, the master and remote units may be widely separated and a telephone circuit between the units is used for enabling the operators to compare lamp indications. The motor M-1 comprises a main field winding F-1 and shaded pole windings F-2-F-3; the winding F-3 is permanently short-circuited and when relay K-1 is energized the torque of F-2 opposes that of F-3 and rotor 55 quickly stops.