Introduction

Doorbells, buzzers and chimes are essential, particularly if you live in a flat. Without some way of attracting your attention, visitors, post and other deliveries can end up standing for hours on the doorstep. Whether you choose a simple 'one note' buzzer or a set of chimes that plays a medley of your favourite tunes, installation is very straightforward.

The 'bell' can be positioned anywhere convenient as long as it is not over a source of heat. For the most part, the bell is usually in the entrance hall so it can be heard throughout the house. Doorbells are generally the 'trembler' type: when power is supplied to the bell it activates an electro-magnet that causes the striker to hit the bell. This can be battery or mains-transformer operated.

Buzzers work in the same way, except that a striker hits the magnet instead of a bell. Chimes have two tubes or bars tuned to different notes and between them is a wound coil known as a solenoid, which acts like a magnet. When the bell push is depressed, a spring-loaded plunger in the solenoid strikes against one tube to release a note. When the bell push is released, the spring throws the plunger against the other tube to make the second note. There are also chimes with microprocessors built in, which will provide you with a whole range of different tunes.

Bell Pushes

Bell pushes are switches that are only 'On' when someone presses them. Inside the push are two contacts to which the circuit wires are connected. One contact is spring-loaded so that when the bell push is depressed it completes the circuit. When the bell push is released, it springs back to its 'rest' position, breaking the circuit. The little light that you often see on bell pushes is 'On' continuously, and has to be supplied by mains power because, even though it's just a tiny bulb and a trickle of charge, it would soon drain a battery. You can also get luminous 'glow in the dark' bell pushes that don't require power.

Batteries and Transformers

As well as a choice of sounds, you can install a doorbell that is battery or transformer operated. Some bells and chimes have a battery or batteries housed inside their casing, while others are operated by a built-in transformer, which reduces the 240-volt mains power to a lesser voltage needed for the equipment.

The battery, bell and bell push are connected by fine insulated 'bell wire'. Because it is generally two-core wire and very fine, it is most often surface run - along the top of skirting boards or in the angle between the wall and ceiling. Bell wire also connects a transformer to a bell and bell push. The transformer is connected to a junction box or ceiling rose in a lighting circuit with 1 mm sq. two-core and earth cable. On a ring circuit, a spur is run in 2.5mm sq. two-core and earth cable to an unswitched fused connection unit fitted with a 3-amp fuse, then with 1 mm sq. two-core and earth cable from the unit to the transformer 'mains' terminals. If, on the other hand, you have a spare 5 amp fuse way in your consumer unit, you could run 1 mm sq. two-core and earth cable from this to the transformer 'Mains' terminals.

If you are uncertain about undertaking any electrical work, there are also 'wireless' doorbell systems, which are operated by batteries inside the bell push and in a receiving sounder unit. The two components generally have to be placed in a straight line with each other and within an optimum receiving distance.

Fitting The Doorbell

To fit your doorbell, you will have to drill a small hole in the doorframe and pass the bell wire through to the outside. Buy a kit that includes full manufacturer's instructions.