High security lock

An improved electromagnetic locking apparatus of the type which includes a lock portion and a removable key portion, the key portion providing a determined unlocking combination signal, the lock portion having an electromotive device for providing a desired unlocking function in response to an unlock voltage signal presented through a switch contact arrangement provided by selective activation of a plurality of switches in response to the placement of the key portion on a determined surface location of the lock portion coincident with presentation of the determined unlocking combination signal, the plurality of switches including at least one switch for providing a signal manifestation in response to the proximate placement of the key portion within the determined surface location of the lock portion, wherein the improvement comprises:

• time delay means, responsive to the unlock voltage signal and to the signal manifestation, for providing, at the end of a determined time interval following presentation of the unlock voltage signal, a gate signal in response to the simultaneous presence of the unlock voltage signal and the signal manifestation during the determined time interval;
• and
• switch means, interconnected between the switch contact arrangement provided by the plurality of switches and the electromotive device, and selectively operable in a first state or a second state in response to the presence or absence of the gate signal from said timing means, said switch means presenting the unlock voltage signal to the electromotive device when operated in the first state in response to the presence of a gate signal, said switch means not presenting the unlock voltage signal to the electromotive device when operated in a second state in response to the absence of a gate signal.