Communications: electrical – Condition responsive indicating system – With particular system function
Patent
1977-12-01
1980-05-13
Caldwell, Sr., John W.
Communications: electrical
Condition responsive indicating system
With particular system function
340503, 340502, 340511, 340661, 340657, G08B 2900
Patent
active
042030951
ABSTRACT:
For monitoring the supervisory current in a communications line between a power source and a protected premises which forms a security protection circuit, monitoring apparatus utilizes sensitive solid state circuitry which appears transparent to the protection circuit. An operational amplifier input circuit protects the circuitry against component damage due to lightning, inherently rejects common mode errors due to noise, transients, and varying power supply voltage, and had an adjustable offset for line length compensation and circuit standardization. Voltage comparator circuitry indicates by digital signals the supervisory current level. After the operator conditions the apparatus for an abnormal current level which has been signalled, a lamp which blinks at a discernable rate is used to serve as a reminder of this state. Filtering circuitry detects and indicates the presence of a predetermined frequency oscillating current imposed in the communications line at the protected premises, producing a digital output. A plurality of such digital outputs may be conveniently processed by a microprocessor.
REFERENCES:
patent: 3454787 (1969-07-01), Gelernter
patent: 3582925 (1971-06-01), Porter
patent: 3641547 (1972-02-01), Reiss
patent: 3673588 (1972-06-01), Riff
patent: 3786501 (1974-01-01), Marnerakis
patent: 3801972 (1974-04-01), Hokim et al.
patent: 3976985 (1976-08-01), Schalow et al.
Caldwell Sr. John W.
Crosland Donnie L.
Potter Electric Signal Co.
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