# US 4,394,703 A · Load protecting arrangement > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,394,703 A - Document ID: US4394703A - Status: Granted - Kind: A - Application number: 06/334,188 - Filed: 1981-12-24 - Granted: 1983-07-19 - Earliest claimed: 1981-12-24 - Assignees: GTE Automatic Electric Labs Inc. - Inventors: James S. Butcher - Web page: https://patentgrep.com/patent/US4394703A ## CPC - H02H 3/087: for DC applications - H02H 3/06: with automatic reconnection - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) ## Abstract A protecting arrangement is dislcosed for multiple loads supplied from a single DC power source. Each load is monitored by a separate protection circuit. Detection of an over-current condition associated with one of the loads will cause the associated protection circuit to assume a non-conducting state and provide a visual indication of same. Periodically enabled common reset means are provided to restore conduction to non-conducting protection circuits following removal of the cause of over-current. ## Claims ### Claim 1 A protection circuit for use between a first source of DC power and a load, comprising: current pass means connected between said load and said DC source; DC bias means connected to said current pass means, conditioning said current pass means to conduct therethrough, current from said first DC power source to said load; sensing means connected to said current pass means; control means connected to said sensing means and to said current pass means, initially operated in response to detection of a flow of current in excess of a predetermined value, from said first source to said load by said sensing means, to operate said current pass means to limit the flow of current therethrough; feedback means connected between said current pass means and said control means, developing a signal in response to said limiting of current flow through said current pass means, to render said control means fully operated, and render said current pass means inoperative; and reset means operated in response to said rendering of said current pass means inoperative, to disable said feedback means developed signal to thereby render said current pass means reoperated. ### Claim 2 (depends on 1) A protection circuit as claimed in claim 1 wherein: said current pass means is a bipolar transistor. ### Claim 3 (depends on 1) A protection circuit as claimed in claim 1 wherein: said control means is a bipolar transistor. ### Claim 4 (depends on 1) A protection circuit as claimed in claim 1 wherein: said feedback means comprises a resistor and a diode connected in series. ### Claim 5 (depends on 4) A protection circuit as claimed in claim 4 wherein: said diode is a light emitting diode providing a visual indication of the state of said current pass means. ### Claim 6 (depends on 1) A protection circuit as claimed in claim 1 wherein: said sensing means further includes isolation means functioning to direct the signal developed by said feedback means to said control means. ### Claim 7 (depends on 6) A protection circuit as claimed in claim 6 wherein: said isolation means comprises a resistor. ### Claim 8 (depends on 1) A protection circuit as claimed in claim 1 wherein: timing means is provided connected to said feedback means, and operated to delay said signal developed by said feedback means, for at least a minimum predetermined time before rendering said current pass means inoperative. ### Claim 9 (depends on 8) A protection circuit as claimed in claim 8 wherein: said timing means is a capacitor. ### Claim 10 (depends on 1) A protection circuit as claimed in claim 1 wherein: said bias means is a second DC power source. ### Claim 11 (depends on 1) A protection circuit as claimed in claim 1 wherein: said reset means is a bipolar transistor. ### Claim 12 A protection circuit for use between a first source of DC power and a load, comprising: current pass means connected between said load and said DC source; DC bias means connected to said current pass means, conditioning said current pass means to conduct therethrough, current from said first DC power source to said load; sensing means connected to said current pass means; control means connected to said sensing means and to said current pass means, initially operated in response to detection of a flow of current in excess of a predetermined value, from said first source to said load by said sensing means, to operate said current pass means to limit the flow of current therethrough; and feedback means including a light emitting diode connected between said current pass means and said control means, developing a signal in response to said limiting of current flow through said current pass means, to render said control means fully operated, and thereby render said current pass means inoperative, said light emitting diode operated in response to said feedback means developed signal to give a visual indication of said pass means inoperative condition. ### Claim 13 A load protecting arrangement for use with a first DC power source and a plurality of loads, including periodically enabled reset means, and a plurality of protection circuits, each connected between said first source and an associated one of said loads and each comprising: current pass means connected between said load and said DC source; DC bias means connected to said current pass means, conditioning said current pass means to conduct therethrough, current from said first DC power source to said load; sensing means connected to said current pass means; control means connected to said sensing means and to said current pass means, initially operated in response to detection of a flow of current in excess of a predetermined value, from said first source to said load by said sensing means, to operate said current pass means to limit the flow of current therethrough; feedback means connected between said current pass means and said control means, developing a signal in response to said limiting occurred flow through said current pass means, to render said control means fully operated, and thereby render said current pass means inoperative; and signal blocking means connecting said feedback means to said reset means, operated to conduct said feedback means developed signal to said reset means but block signals from any other ones of said protection circuits; said enabled reset means operated, in response to said rendering of at least one of said current pass means inoperative, to disable said associated control means and thereby render said current pass means reoperated. ### Claim 14 (depends on 13) An arrangement as claimed in claim 13 wherein: said reset means is a bipolar transistor connected to a source of periodic pulses and said signal blocking means comprises a diode. ### Claim 15 (depends on 13) An arrangement as claimed in claim 13 wherein: said sensing means further includes isolation means, functioning to direct the signal developed by said feedback means to said control means; and timing means connected to said feedback means, operated to delay said signal developed by said feedback means for at least a minimum predetermined time before rendering said current pass means inoperative. ### Claim 16 (depends on 15) An arrangement as claimed in claim 15 wherein: said isolation means comprises a resistor and said timing means comprises a capacitor.