This is a dual input type code lock system. One code activates one relay and another code activates another relay.
http://www.webx.dk/oz2cpu/pic/piccode.htm
PIC16F84 based
http://www.vermontficks.org/combo2s.gif
uses PIC16F84
http://jap.hu/electronic/combination_lock.html
built with PIC12C508
http://jap.hu/electronic/door.html
Differently from the usual combination locks, this circuit replaces RF remote controls. Enter the correct combination to transmit a code compatible with the popular remotes based on the MM53200, UM3750 and UM86409.
http://www.riccibitti.com/rf_pad.htm
These software keys can open gates, garages, TV sets, telephones, VCRs, well pumps... In practice this circuit is capable to lock or time all the devices that can be connected to relays.
http://www.nutchip.com/progetti/combinazione_en.htm
http://circuitos.tripod.cl/schem/r86.gif
The circuit above above makes use of the CMOS 4017 decade counter IC. Each depression of a switch steps the output through 0 - 9. By coupling the output via an AND gate to the next IC, a predefined code has to be input to create the output.
http://www.zen22142.zen.co.uk/Circuits/Switching/diglock.htm