Chip card as security key

The “chip card” consists of a small board on which an integrated circuit, IC1, forms the key. The logic circuit for the key is hard-wired. The inputs and outputs of this circuit are terminated in a socket, St1. It is, of course, advisable to use a surface-mount device (SMD) for IC1 (as well as for the other ICs in the circuit) and a microminiature or miniature type of socket (and matching plug, Bu1), to keep the safety key as small as possible.