# US 4,398,098 A · Electronic latching circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,398,098 A - Document ID: US4398098A - Status: Granted - Kind: A - Application number: 06/371,912 - Filed: 1982-04-26 - Granted: 1983-08-09 - Earliest claimed: 1982-04-26 - Assignees: NCR Corporation - Inventors: Jerry M. Minchey - Web page: https://patentgrep.com/patent/US4398098A ## CPC - H03K 17/22: Modifications for ensuring a predetermined initial state when the supply voltage has been applied (bi-stable generators H03K3/12) - H03K 17/30: Modifications for providing a predetermined threshold before switching (shaping pulses by thresholding H03K5/08) - H03K 2017/226: {in bipolar transistor switches} - H03K: PULSE TECHNIQUE (measuring pulse characteristics G01R; modulating sinusoidal oscillations with pulses H03C; transmission of digital information H04L; discriminator circuits detecting phase difference between two signals by counting or integrating cycles of oscillation H03D3/04; automatic control, starting, synchronisation or stabilisation of generators of electronic oscillations or pulses where the type of generator is irrelevant or unspecified H03L; coding, decoding or code conversion, in general H03M) ## Abstract An electronic latching circuit is described for incorporation into an electronic equipment which includes a battery, a load and a power supply. During shipment or storage of the equipment, the electronic latching circuit electrically isolates the battery from the load. The first time that the equipment is put into operation and turned on after shipment or storage, the electronic latching circuit automatically permanently connects the battery to the load. Once connected to the load the battery remains connected to the load, even when the equipment has a power failure, the power supply fails or the equipment is turned off. In a preferred embodiment the electronic latching circuit comprises: switching means for electrically isolating the battery from the load when the switching means is disabled and for connecting the battery to the load when the switching means is enabled; and input means connected to the battery and to the switching means for disabling the switching means until the power supply is initially energized and being responsive to the initial energization of the power supply for permanently enabling the switching means to connect the battery to the load. ## Claims ### Claim 1 In an electronic equipment which includes a battery, a load and a power supply, an electronic latching circuit comprising: switching means for electrically isolating the battery from the load when said switching means is disabled and for connecting the battery to the load when said switching means is enabled; and input means connected to the battery and to said switching means for disabling said switching means until the power supply is initially energized and being responsive to the initial energization of the power supply for automatically permanently enabling said switching means to connect the battery to the load. ### Claim 2 In an electronic equipment which includes a battery, a load and a power supply, an electronic latching circuit comprising: switching means connected between the battery and the load and being responsive to a first voltage level for electrically isolating the battery from the load and being responsive to a second voltage level for connecting the battery to the load; and input means connected to the battery and to said switching means for developing the first voltage level until the power supply is initially energized, said input means being responsive to the initial energization of the power supply for developing the second voltage level to automatically permanently enable said switching means to couple the battery to the load. ### Claim 3 (depends on 2) The electronic latching circuit of claim 2 wherein said switching means includes: an amplifying device having an input circuit connected to said input means and an output circuit serially connected between the battery and the load. ### Claim 4 (depends on 3) The electronic latching circuit of claim 3 wherein said input means includes: a first resistor; and a fuse serially-connected to said first resistor at a common junction to which the power supply and said input circuit are also coupled, said serially-connected first resistor and fuse being connected across the battery to enable the first voltage level to be developed at the common junction until the power supply is initially energized, said fuse being blown by current flow therethrough from the power supply when the power supply is initially energized to thereby cause the common junction to rise to the second voltage level to permanently enable said switching means to connect the battery to the load. ### Claim 5 (depends on 2) The electronic latching circuit of claim 2 wherein said switching means includes: first and second transistor circuits each having an input circuit and an output circuit, said input circuit of said first transistor circuit being connected to said input means, said output circuit of said first transistor circuit being connected to said input circuit of said second transistor circuit, said output circuit of said second transistor circuit being serially connected between the battery and the load. ### Claim 6 (depends on 5) The electronic latching circuit of claim 5 wherein said input means includes: a first resistor; and a fuse serially-connected to said first resistor at a common junction to which the power supply and said input circuit of said first transistor circuit are also coupled, said serially-connected first resistor and fuse being connected across the battery to enable the first voltage level to be developed at the common junction until the power supply is initially energized, said fuse being blown by current flow therethrough from the power supply when the power supply is initially energized to thereby cause the common junction to rise to the second voltage level to permanently enable said switching means to couple the battery to the load. ### Claim 7 (depends on 4, 6) The electronic latching circuit of claim 4 or 6 wherein said input means further includes a second resistor connected between the power supply and the common junction to limit the current through said fuse and to prevent the power supply from latching off during the initial energization of the power supply due to excess current. ### Claim 8 In an electronic equipment which includes a battery, a load and a power supply, an electronic latching circuit comprising: a switching circuit having an output circuit connected between the battery and the load and an input circuit, said switching circuit being responsive to a first voltage level applied to said input circuit for electrically isolating the battery from the load and to a second voltage level applied to said input circuit for connecting the battery to the load; a common junction to which said input circuit is connected; first and second resistors, said first resistor being connected between the power supply and said common junction; a fuse serially-connected to said second resistor at said common junction, said serially-connected second resistor and fuse being connected across the battery to develop the first voltage level at said common junction until the power supply is initially energized, said fuse being blown by current flow therethrough from the power supply by way of said first resistor when the power supply is initially energized to thereby cause said common junction to rise to the second voltage level to automatically permanently enable said switching means to connect the battery to the load.