Door security entry system - with information pulses transmitted between door and door frame using transmitter and receiver with logic circuits

摘要

The door entry system, for an apartment building etc. has a unit for transmitting information between the frame of the door and the door itself, e.g. to allow a lock to be released. The information is transmitted via a magnetic or opto-electronic circuit as a series of pulses of variable duration according to the type of information. Each received pulse is compared with pulses each having a duration greater than the time constant assigned to the transmitted pulse e.g. double this time constant, so that only pulses corresponding to this time constant are validated.