Tip and ring conductor voltage tester

Abstract

A circuit-energized voltage tester for determining whether or not the voltages on the tip and ring conductors of a telephone line are within their normal ranges is disclosed. The voltage tester is adapted for inclusion in a standard telephone repairman's handset and includes an energy storage circuit that becomes charged upon the application of handset test probes to tip and ring conductors if they are carrying a voltage greater than a predetermined level. Upon the closure of a switch, the energy thus stored energizes the remaining portion of the voltage tester. If suitable voltages are present on the tip and ring conductors, light emitting diodes forming a portion of a pair of optical isolators are controlled such that no measurement indication is provided. Specifically, the photo transistor portions of the optical isolators are alternately interrogated by a low frequency measurement control oscillator. The results of the interrogation control the generation of either high or low frequency tones produced by a single audio oscillator. The measurement control oscillator also controls the audio oscillator such that one tone may be generated when the first photo transistor is interrogated and the other tone may be generated when the second photo transistor is interrogated. The tones are only generated when the tip and ring voltages fall outside of their normal ranges. Thus, the absence of any tone indicates that both tip and ring voltages are in their normal ranges and the presence of one or both tones indicates that either one or both of the tip and ring voltages is outside of its normal range.