Communications: electrical – Systems – Call station
Patent
1975-12-05
1976-10-19
Caldwell, John W.
Communications: electrical
Systems
Call station
340255, G08B 2100
Patent
active
039874257
ABSTRACT:
The circuit is adaptable for electric apparatus, particularly trolley buses and the like, where the apparatus derives its power from a pair of electric power lines, and the body of the apparatus is insulated from ground. One of the pair of electric power lines is at, or very nearly at, ground potential. The circuit provides a known test resistance interposed between the body of the apparatus and the most negative of the power lines so that the test resistance is effectively in series with the leakage resistance between the electric power lines; thereby permitting a measurement between the body of the apparatus and the most negative of the power lines to determine current flow through the known resistance greater than a predetermined minimum. When the current flow through the known resistance is higher than the predetermined minimum, the body of the apparatus is at a voltage above ground sufficient that a hazardous condition might exist, and an alarm status is initiated. The alarm circuits include a first delay circuit to accommodate transient voltage swings between the power lines which would normally be shorter than a predetermined period of time; and a second delay circuit having a longer predetermined period of time so that if an alarm status continues for the second predetermined length of time, an alarm indication is latched on.
REFERENCES:
patent: 1394642 (1921-10-01), Quass
patent: 2658191 (1953-11-01), Stolp
patent: 2727203 (1955-12-01), Zeitlin et al.
patent: 3383522 (1968-05-01), Apfelbeck et al.
Caldwell John W.
Electronic Surveillance Corporation
Myer Daniel
LandOfFree
Leakage resistance detector and alarm circuit does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Leakage resistance detector and alarm circuit, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Leakage resistance detector and alarm circuit will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-105884