External hardware is not strictly within the scope of Beltower software, but a few hints are offered here.

Single Signal

Single signal mode is recommend, especially for use with Raising & Lowering and multi-bell interfaces (Belfree or Bagley).   It requires a single actuator for each bell, positioned (on the wheel) beside the sensor (on the frame) when the bell is down.   A signal will be raised as the actuator passes the sensor, on each stroke, when the bell mouth is at bottom dead centre.

Twin Signals

Twin actuators have limited functionality but should be fixed at about 120 degrees either side of the sensor box (each about a third of the circumference apart).   A signal will be raised as each actuator passes the sensor, on each stroke, ideally, timed to coincide with the clapper strikes.


Make sure, when positioning each actuator, that the bell is at bottom dead centre, and make allowance for things like the weight of the stay or the rope, which might pull the bell off centre.   It might also be necessary to re-adjust the position to allow for any odd struckness.

You will need a power supply (usually +9v or +5v) and cable to connect to the sensors and to bring the signals back to the computer, plus terminals at the sensor, and a plug to connect to the PC.   It is also useful to have a terminal block at the PC to allow easy wiring changes.

At the sensor	a 3 pin plug+socket or screw terminal block, either inside, fixed to the outside or trailing,
In the bell chamber	a screw terminal block or an MBI box if appropriate, for distribution to/from multiple sensors,
At the PC	a 9 pin D Socket (female plug) with Hood,   plus optional terminal block,
Cable	either 3 core (+9v, signal, Gnd) for each sensor,   or multi-core for multiple sensors. The cables should be screened to avoid interference from flourecent tube starters, clock winders etc., and you should consider using individually screened signal wires, if installing more than one sensor, to avoid cross-talk.

These are likely to cost between £20 and £60, depending on the distance and the number of sensors.