GB940142A - Improvements in circuit testing apparatus - Google Patents

Abstract

940,142. Visible signalling apparatus. A. S. ERIKSSON. March 10, 1960 [March 12, 1959], No. 8423/60. Heading G4F. In apparatus for testing the continuity of a circuit, comprising an electromagnet and a battery, a make and break contact operated by the electromagnet serves in general as an audible signal, while a neon type lamp operated by the high voltage induced in the coil of the electromagnet at the periodic "break" of its circuit effected by the make and break contact, serves as a visible flashing signal if the circuit under test is continuous. The neon 3 (Fig. 1) is connected in parallel with the electromagnet 5 which is in series with a battery 4, make and break contact 2,output leads 18, 20 and thus the circuit under test. The neon 3 may be connected between one end of the electromagnet (Fig. 2 not shown) and the output lead 18 remote from the electromagnet 5. A further alternative uses a two way switch 21 (Fig. 3) so that when the switch is in the dotted position the operation is the same as for Fig. 1 but with switch 21 in the other posiare connected with the internal wiring by means of contact plates 34, 35 and an insulated clamp 36. Screw 37 serves to tighten the clamp against the leads and the contact plates and also forces tion, high resistance e.g. 50kc, circuits may be tested, the induced e.m.f. in this case flowing through the test circuit and then through the neon. The make and break contacts 8, 9 (Fig. 5), armature 7, electromagnet coil 6 and core 5, the neon 3 and battery 4 are attached to a baseplate 22 contained in a housing 24. The output leads 18, 20 the lower part 41 (Fig. 8) of the clamp against an outer conduit 31 of the output leads 18, 20 and an abutment 43 of the baseplate 22, thus preventing the output leads 18, 20 from being inadvertently pulled out of the apparatus and also preventing the ingress of dust and other foreign matter into the apparatus.