MODEM LOOP CURRENT DETECT SYSTEM TO DETECT AN OFF-HOOK CONDITION IN AN EXTENSION TELEPHONE

A telephone line monitoring circuit uses an optoisolator (OPTO 2) to convert the telephone line current to a voltage which is applied to the input of an A/D converter (118). The A/D values are coarse values representing telephone line current. The A/D is sampled at a predetermined interval to identi...

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Bibliographische Detailangaben
1. Verfasser:	PITSCH, ROBERT ALAN
Format:	Patent
Sprache:	eng ; fre
Schlagworte:	BASIC ELECTRONIC CIRCUITRY CALCULATING COMPUTING CONVERSION OR DISTRIBUTION OF ELECTRIC POWER COUNTING ELECTRIC COMMUNICATION TECHNIQUE ELECTRIC DIGITAL DATA PROCESSING ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR ELECTRICITY EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS GENERATION HANDLING RECORD CARRIERS NATURALLY-OCCURRING ELECTRICITY PHYSICS PRESENTATION OF DATA PULSE TECHNIQUE RECOGNITION OF DATA RECORD CARRIERS SELECTING SELECTING RESONANT CIRCUITS STATIC ELECTRICITY TELEPHONIC COMMUNICATION TRANSMISSION TUNING RESONANT CIRCUITS
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Beschreibung
Zusammenfassung:	A telephone line monitoring circuit uses an optoisolator (OPTO 2) to convert the telephone line current to a voltage which is applied to the input of an A/D converter (118). The A/D values are coarse values representing telephone line current. The A/D is sampled at a predetermined interval to identify changes introduced by the telephone company central office, and to take thos e changes into account when deciding if an extension telephone has gone off- hook. When a customer causes an extension telephone to go off-hook, the line current divides between the extension telephone and the IRD modem (100), and such change is detected.