Our plans to use a sound generating electrical device in the circuit have been thwarted. We searched high and low for a suitable device. Various alarms and buzzers (including, components retrieved from the innards of plush toys) were considered. Unfortunately, none of them generated a telephone or siren type sound. In a last ditch effort, I attempted to build an electronic siren from an electronics kit called "Funway into Electronics, Volume 1". Project number six promised the elusive sound of "An electronic siren". It even had a drawing of a police car. Believing a solution was at hand, I spent several hours happily assembling it (to be honest, I became increasingly frustrated trying to identify the components required to complete it). In the end, however, it was complete (see picture below).
I then hooked it up to a 9V cell and was greeted by a barely audible sound I still have trouble finding words to describe. Let's just say it sounded nothing like a siren.
Without a suitable sound device it was agreed that the circuit would be modified to include a switch as the third component.
Voron, S. & Tester, R. (2002) Funway into Electronics, Volume 1. Chullora, NSW: Dick Smith Electronics Pty Ltd.
