US 4,903,323 A · Call box

Abstract

A communication system having a base station and a number of field units employs a virtual hold technique and a self-testing technique. In the virtual hold technique, when a field unit is put on hold, the communication channel previously used by the field unit is released for use elsewhere in the system, thereby increasing the efficiency of the system. In the self-test technique, a test signal is transmitted to the field unit where it is applied to the earpiece of a handset so as to generate sound waves which are picked up by the microphone in the mouthpiece of the handset and transmitted back to the base station for comparison with the original test signal. In this manner, the entire communication loop is tested without the need for human intervention, and in particular without the need for a person to be present at the field unit. The self-test technique improves the reliability of the system.

Claims8

Dependent claims

A method of testing a two-way radio communication channel between a base station and a distant radio telephone and noteworthy for not needing anyone to be present at the distant radio telephone, comprising the steps of:

(a) generating a test signal in the audio frequency range;
(b) transmitting the test signal from the base station to the distant radio telephone via the communication channel being tested;
(c) receiving at the distant radio telephone the test signal transmitted from the base station;
(d) detecting the test signal received by the radio telephone;
(e) applying the detected test signal to the earpiece of the radio telephone, whereby the earpiece produces a sound that is sensed by the mouthpiece and converted to an electrical signal;
(f) transmitting the electrical signal produced by the mouthpiece from the radio telephone to the base station via the communication channel being tested;
(g) receiving at the base station the electrical signal transmitted from the radio telephone;
(h) detecting the electrical signal received at the base station;
and,
(i) deciding whether the detected electrical signal is similar to the test signal that was transmitted by the base station.

7 more elements

Dependencies are inferred from the claim text.

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Abstract

Claims8