Test apparatus to check conditions and characteristics of power and communication networks

Claim 1

Test apparatus to check or test the condition or network characteristics of electrical networks, selectively, for continuity; transmission characteristics; signals thereon, said test apparatus having an audio frequency generator (T1, T2, 1-4, 9); an audio reproducer (L1); a local battery (B); test terminals (P+, P-) for connection to the network to be checked or tested; and switch means (S, U) for selectively interconnecting the test terminals and to the audio reproducer, and wherein, in accordance with the invention, the apparatus includes a protective circuit (C5, 12, D1, D2, K, TF, I, II) included in circuit with the test terminals (P+, P-), and at least one of: the tone generator, the audio reproducer; an audio amplifier (T3, T4) coupled to the audio reproducer (L1, L); and wherein (a) if continuity through the network, when connected between the test terminals (P+, P-) is to be determined and, further, if continuity is established, the resistance between the test terminals is to be determined, the switch means connect the audio frequency generator (T1, T2, 1-4, 9) to the test terminals (P1, P2), the audio frequency generator to the local battery (B) to energize the audio frequency generator, and the audio frequency generator to the audio reproducer, whereby the audio frequency generator will operate at frequencies determined by the resistance of the network and, upon open circuit of the network, will be inoperative, and no tone will be reproduced; (b) to test transmission of a-c frequencies through the test terminals (P+, P-) into the network, the switch means (U, S) selectively connect the audio frequency generator (T1, T2, 1-4, 9) to the test terminals; the audio frequency generator to the local battery (B) for energizing the audio frequency generator and to transmit audio frequencies into the network to permit monitoring of said audio frequencies transmitted into the network and to determine if the audio frequencies are propagated therethrough; and (c) to test propagation through the test network of audio frequencies transmitted therein, the switch means selectively connect the audio tone receiver including the amplifier to said test terminals (P1, P2), and interrupt connection from the frequency generator (T1, T2, 1-4, 9) to the tone receiver and to at least one test terminal.