Tristable circuit with well defined triggering threshold

A new tristable circuit is described. It is basically an Eccles-Jordan circuit arranged to have a third stable state in which both transistors operate in the active region. Switching from this centre-stable state to either of the other two states can be arranged to occur at a well defined level of triggering current. The circuit is particularly suitable for use as an output latch with certain types of digital-computer store or in ternary-logic circuits. The effects of component and supply-voltage tolerances are discussed.