Extended input facilities

Another instance where multiple inputs to a single gate operation can occur is with certain types of gate elements that have an 'EXTENDED INPUT' facility provided. The circuit illustrated in Figure is a typical example showing a 3 input NAND gate (element X) using isolating diodes in each of the input lines A, B and C. A connection from the base of the transistor is brought out in order that further inputs (element Y) can be connected to extend the input range (i.e. inputs D and E). When this configuration is employed in a logic circuit the approved form of symbol to be used is shown on the right, with an arrow indicating that the connection is made to an extended input facility at element X.