elekdoorbell

Gone are the days of the simple `ding-dong` doorbell (` Avon calling .. .`). Many modern house-holders seem to want doorbells that play anything from the 1812 Overture to a slightly abridged version of Handel`s Messiah. Unfortunately, most commercially available programmable doorbells, and in particular those which are microprocessor-control led, are anything but cheap (£ 20 is not uncommon). For this reason we decided it would be nice to design a programmable doorbell which could be built for around a fiver. The result of our efforts -the `Elekdoorbell` -is capable of playing almost any desired tune up to 128 notes in length. The circuit can be mounted on a single board, and the current consumption is extremely low, so ~hat an existing bell transformer can be used for the power supply.