Communications: electrical – Systems – Call station
Patent
1975-06-25
1976-11-30
Swann, III, Glen R.
Communications: electrical
Systems
Call station
315129, 340 52R, G08B 2100
Patent
active
039952622
ABSTRACT:
A core of magnetic material in the shape of a closed loop has three windings thereon. The first winding forms a circuit with a lamp to be monitored. As long as the lamp's filament is intact, whether or not the lamp is energized, this circuit can conduct current. The second winding is connected to a pulse generator to induce variations in the magnetic flux in the core. The third winding detects these variations in flux and a detection circuit connected to the third winding produces an indication if the variations are greater than a predetermined threshold. If the lamp is energized, the current in the first winding causes the core to be saturated with magnetic flux and thus the induced flux variations are below the detection threshold. If the lamp is unenergized, but intact, the current pulses in the second winding induce counter-pulses in the first winding which counteract the effect of the pulses in the second winding and thus the induced flux changes are below the detection threshold. If the lamp filament is broken, the pulses in the second winding will produce a sufficient change in flux in the core to be detected. Thus a defective lamp is detected whether or not it is energized. A second embodiment monitors two lamps with one core.
REFERENCES:
patent: 3183498 (1965-05-01), Midis et al.
patent: 3417310 (1968-12-01), Hill
patent: 3624630 (1971-11-01), Schroeder
patent: 3898513 (1975-08-01), Kopernik et al.
France George
Watts Jack
Swann III Glen R.
Welwyn Electric Limited
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