Cable locator with parallel LC tuned circuit - has inductance in probe head to sense signal transmitted down lost cable

摘要

An apparatus for locating electric cables such as phone lines comprises a frequency generator connectible between one end of the line and earth and a detector for detecting the opposite line end. The detector includes a parallel resonant circuit formed by a capacitor (C2) and inductor (L2), the latter being located in a head (22B) coupled to a housing (21) containing the remainder of the circuitry. The resonant circuit is connected to an amplifier (A3) and diode detector (D1) in turn connected to a twin threshold trigger circuit (A4) which controls a display of three light-emitting diodes (4-6). The head is rounded and forms the tip of an arm (22A) detachably mounted on the housing to enable the head to be inserted into a bundle of cables. A potentiometer on the detector output allows sensitivity adjustment.