Abel can be used in the tower where the bells are tied and Abel is used to produce the bell sounds in the ringing chamber. There are essentially two ways you can use Abel: either as a simulator, where you use one or two tied bells and Abel rings the rest; or as a sound generator (true "silent practice"), where all the bells are tied and Abel is used only to generate the bell sounds.

For both simulator and silent-practice operation, the bells must have sensors attached to them so that Abel can detect when the bell would normally strike. If you are using one of David Bagley's "Multi-bell interfaces" to connect to Abel, David will advise on sensors for use with it. Otherwise, you can make your own sensors: making sensors to attach to bells is not difficult, though you will need to be competent with a soldering iron. There may also be commercially-produced sensors available (but not from the suppliers of Abel) that may be appropriate for connecting to PCs.

If you are doing a tower installation of Abel, it is up to you to comply with all regulatory standards for wiring (including standards about proximity of mains-connected devices and wiring to lightning conductors, to which metal bell frames are often bonded), church rules for changes to the building, etc. The authors of Abel, and AbelSim Ltd, are not responsible for work you do in the tower, and do not guarantee that the circuits given in Abel documentation can be made to conform to any such rules and regulations.

There are at least four categories of sensor you can use. Which ones are suitable for your belfry depends much on local technical skills, and how weather- and light-proof the belfry is.

• Simple switch based sensors. Typically, these are magnetic reed-switches fastened to the frame, actuated by magnets attached to the wheel. These are simple to build, though the magnets must be powerful enough to operate the reed switches reliably, and clearly must be securely fastened to the wheel! They are extremely cheap and simple, but the magnets usually need to pass very close to the reed switches, which can cause problems if the wheels are warped.
• Optical sensors. These can use either visible light or (usually) infrared. They tend not to be suitable if there is a lot of light or reflections in the belfry, as stray reflections can confuse even infrared devices. They are however fairly inexpensive to make, and the reflectors that have to be fastened to the wheel are very lightweight, so there is no risk of them becoming detached during ringing and causing damage.
• Proximity detectors. These are extremely reliable. They operate on the same principle as a metal detector. They use special detector chips and specially-made tuned-circuit "actuators" attached to the wheel. Like the optical reflectors, the components that need to be attached to the wheel are very lightweight.
• Motion detectors.

Click on the following items for instructions on how to make bell sensors to proven designs:

  Optical sensors
  Proximity sensors

See also:

  Connecting bells using the serial port
  Connecting bells using the Multi-Bell Interface
  Handbells as external bells
  Using external control switches with Abel
  Configuring Abel to use bell sensors
  Configuring Abel to use control switches