Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1979-09-17
1981-06-09
Caldwell, Sr., John W.
Communications: electrical
Condition responsive indicating system
Specific condition
250221, 340523, G08B 1318
Patent
active
042727626
ABSTRACT:
Sensing apparatus for monitoring the passage of objects, including people, through a doorway. A source of radiant energy is positioned at one side of the doorway and two spaced-apart detectors are positioned at the opposite side to receive beams of radiant energy from the source. A receiver is connected to each detector and produces a signal indicating whether the beam of radiation from the source is impinging on its associated detector or is being blocked by a passing object. Logic circuitry responds to the signals from the receivers and produces a first or second output condition depending upon which beam from the source is the last one to be interrupted by a passing object. Output circuitry coupled to the logic circuitry produces a pulse at one output terminal on a transition from the first to the second output condition indicating passage of an object through the doorway in one direction and produces a pulse at another output terminal on a transition from the second to the first output condition indicating passage of an object through the doorway in the opposite direction.
REFERENCES:
patent: 2455909 (1948-12-01), Smith
patent: 2595993 (1952-05-01), Templeman et al.
patent: 3524180 (1970-08-01), Cruse
patent: 3789384 (1974-01-01), Akers
patent: 3825916 (1974-07-01), Steele et al.
patent: 3914753 (1975-10-01), Cho
patent: 4009389 (1977-02-01), Lindholm
Geller William L.
Naugle Richard L.
Caldwell Sr. John W.
GTE Laboratories Incorporated
Keay David M.
Nowicki Joseph E.
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