Abstract: Code identification apparatus in which a magnetically coded key or like instrument is inserted into a reader which reads the code on the key. The reader has a guideway to receive the key and, adjacent the guideway, a row of code sensors disposed such that as the key is inserted into the guideway, rows of code locations on the key successively pass the row of code sensors. The reader incorporates signal processing circuitry which determines when there is an output signal from any one or more of the code sensors as a measure of time intervals during which successive rows of code locations are passing the sensors. The signals are accumulated during those time intervals and the accumulated signals registered at their conclusion.

Abstract: Access control system in which a magnetically coded key or card is inserted into a reader which reads the recorded code. The key is coded by small permanent magnets embedded in non-magnetic body of key at positions on a 4 .times. 4 regular grid of possible positions. The reader includes row of 4 Hall Effect sensors adjacent keyway entrance so that the 4 rows of magnet positions pass successively across them. Signals generated in sensors are transmitted to signal storage units and extracted from the storage units on withdrawal of the key. Activation of sensors and transmission of signals is controlled by successive interruption by leading edge of key of light beams along the keyway.