Report Electronic Stethoscope 2 in Projects Q/A Posted November 10, 2004 Audio, Thanks for the quick reply. This may sound dumb but what does TR1 stand for? It looks to me to be a transistor. If it is what type and value would be correct. The use of the 555 was was give a time delay before all the sirens go off. nothing better than to let the intruder think he got in undetected and then when he least expects it everthings goes off, sirens, warning that the police will be there in less then 30 seconds, fake gas release to make him think tear gas has been released and an anounced warning that if he doesn't get out immediately all doors and windows will become electrified with high voltage. This should scare the pants off of any intruder. He should drop everthing and hightail it out of there pronto.But don't worry I won't be using real teargas or electifing the door and windows. I'll just play a tape of nasty electrical discharge and have a CO2 canister release, which will look like gas is being released. I bet he never comes back to my house again. Better to pick a house where he'll feel safe. The mind can be a powerful weapon of defence when it is played out correctly.DelTry out a tube of that special solder. I think you'll find it as good if not better than the stuff you are using. Thanks again for all of your help. If you ever need a chemistry type question answered please feel free to contact me.