Abstract: An electrical keying arrangement ensures that correctly associated electrical components, such as a circuit board and connector, are interconnected by completing a conducting path which includes two pairs of keying terminals positioned on the components. One pair of uniquely spaced and positioned keying terminals on the edge of the circuit board are strapped together to complete the conducting path through the other pair of keying terminals when the board is inserted in the connector. The path is completed only when the connector keying terminals are similarly, uniquely spaced and positioned. When completed, the path may be utilized to energize a relay which controls the application of power to the circuit board.

Abstract: In a telecommunications switching system having a central processor for generating control signals, peripheral units, and a power source terminal, a power control arrangement includes a plurality of power switches for selectively connecting and disconnecting the peripheral units and the power source terminal in order to minimize power consumption. Responsive to peripheral unit control signals, a power control unit, which is included in the arrangement, controls the operation of the power switches so that only those peripheral units designated by a control signal are connected to the power source terminal. After the peripheral units have been operated, the power control arrangement disconnects the operated peripheral units from the power source terminal.