A switch which changes state each time it gets an impulse.
http://www.4qdtec.com/ics.html
Radio Controlled Electronic Switch can be used to switch on/off anything electrical, whatever it is.
http://www.uoguelph.ca/~antoon/gadgets/rc-sw.htm
R/C Timer switch adjustable from 20 - 80 seconds.
http://www.uoguelph.ca/~antoon/gadgets/rc-sw2.htm
may be used instead of servo and mechanical micro switch
http://www.tuug.fi/~isaarine/electronics/rc-switch/
The door opens inserting an electronic card! Very useful also to access private parks, enable photocopiers, activate showers and night light in sport resorts shared between clubs.
http://www.nutchip.com/progetti/card/card_en.htm
The circuit uses an inexpensive C-MOS inverter package and a few small capacitors to drive two power MOS transistors from a 12v to 15v supply.
http://www.discovercircuits.com/DJ-Circuits/fetssr.htm
This circuit demands a control current that is 100 times smaller than that needed by a typical optically isolated solid state relays.
http://www.discovercircuits.com/DJ-Circuits/lowssr2.htm