Electrical timing device

Claim 1

In combination with an electrical plug-in circuit card carrying a circuit having at least one circuit element capable of assuming more than one state, which element must occupy a preferred one of said states before the circuit can be used, which card also carries a first terminal and a second terminal at which reference and power potentials respectively appear when the card is plugged-in at a working position, the improvement which comprises at least one priming bias means for applying a signal responsive to said power potential from said second terminal to at least one of said circuit elements to bias said one element to a preferred state; timing device means responsive to the appearance of said reference and power potentials at said first and second terminals respectively to time a time interval exceeding the time required for said one element to change from one to another of said alternative states, and to produce a switching signal on the expiration of said time interval; and switching device means connected between said priming bias means and said timing device means for terminating the delivery of said signal responsive to the power potential by said priming bias means in response to said switching signal from said timing device means.