Doors and ucontrolers - creative thinking

When I was an undergraduate, I fixed a vibration switch (one of those used for burglar alarms) to my room door (on the inside). Knocking on the door caused that to switch, triggering a monostable. This operated a musical dorobell IC and turnd on some LEDs on the door (set by a switch inside my room) that indicated where I was likely to be foubd... [Actually this was part of a more complex system, including a keyboard on the otuside of the door linked to my OS-9 system so you could leave me a message...] If/wehn I get a house where I can make whatever modifications I like, I am goign to do something like this : Make an 'electric knocker'. This is essemtially an electric bell with the gong replaed by a hollow wooden box. It's shown in 'Harper's Electricity Book for Boys' (this has been reprieted recently, but I have the original). Wire that to the pushbutton on the doorframe Fit a viration swithc to the door, wire that to a monostable an a bell. Thus knocking o nteh door rings the bell, pressing the button causes knocking. And of course put up the obvious sign : 'Please knock if an answer is not requuired'. And see how long it takes poople to run away screaming :-) -tony