Electronic calculator with push-button on-off system

Claim 1

Power switch apparatus for a batteryoperated electronic calculator device having a plurality of pushbutton momentary contact keyswitches, a large-scale-integrated MOS semiconductor device coupled to the keyswitches by a plurality of conductors, electronic circuitry within the device for processing information entered by the keyswitches, a segmented multiple digit display, means for scanning inputs of the display with scan signals, the keyswitches being in a matrix of rows and columns, the columns of the keyswitches being actuated by said scan signals, comprising: a bistable latch circuit continuously powered by the battery, a semiconductor control element in the form of an MOS transistor responsive to the condition of the latch circuit and exhibiting a low impedance when the latch is in one condition and exhibiting a high impedance when the latch is in the other condition, coupling means connecting a first of the keyswitches to the latch circuitry to cause the latch circuit to switch to said one condition upon actuation of the push-button keyswitch, means connecting said electronic circuitry to the battery only through the semiconductor control element, coupling means connecting a second of the keyswitches to the latch circuit to cause the latch circuit to switch to the other stable state upon actuation of the associated push-button, said first and second keyswitches being on the same column, the column upon which the first and second keyswitches appears being actuated continuously by a fixed potential which is different from the potential of the scan signals.