Abstract: An automatic control transfer device for selectively energizing an electrical distribution system from a pair of electrical power sources. The device includes means for sensing electrical conditions on both of the sources and programmable electronic digital logic to selectively energize associated circuit interrupters for switching a distribution system between the two sources. A plurality of time delay functions are provided utilizing a separate oscillator for each function, each oscillator providing input to a common digital counter. The device senses the status of associated circuit interrupters to provide interlocking and lockout functions as well as proper switching commands for either two- or three-circuit interrupter systems. Means are also provided for testing the entire device without initiating an actual source transfer.

Abstract: An automatic transfer control device for selectively energizing an electrical distribution system from a pair of electrical power sources. The device includes voltage sensors for sensing electrical conditions on each of the sources. The device may be used on either three-wire or four-wire systems. The voltage sensors comprise an operational amplifier for artificially generating a phase-to-phase voltage from two phase-to-ground voltages. The artificially generated voltage is used to detect sequence reversal on the sources being monitored. Separate means are provided to select a source from which to draw control power for the device, the control power criterion being different from the transfer criterion.

Abstract: A limit switch utilizing static components and an infrared light emitting diode in conjunction with a photosensitive transistor. A mechanical shutter is provided for insertion between the diode and transistor to interrupt the infrared link therebetween, this will occur when a predetermined limit is reached by an object which is controlled by the limit switch. The limit switch is of the two terminal type, that is it requires no separate source of power for operation than the power in the line being controlled by the switch. It is adapted for high temperature operation.

Abstract: Solid-state digital time delay relay having a pair of complementary contacts one of which breaks or opens before the other of which makes or closes. The switching or transfer function utilizes logic elements for each set of contacts. A multistate indicator is also provided to give one indication of contact status.

Abstract: Solid-state digital time delay relay having a pair of complementary contacts one of which breaks or opens before the other makes or closes. The switching or transfer function utilizes a light emitting diode in conjunction with a photosensitive resistive element for each set of contacts.