Register control

A register stop key acts as a switch.
Each stop key controls one magnet. In the ‘on’ position, low-voltage current is passed to a magnet located in the windchest.

The preset system has two magnetic coils (S) .
This system can also turn the stop key off!

The variety of sounds and colour require pipes built to different scales,
in thickness as well as length, and constructed from different materials such as wood, tin, zinc, copper and other alloys.
Both labial pipes and reed pipes, with or without resonators, are employed.
The organ pipes are examined in more detail in dedicated chapters in the series ‘Technique behind the theatre organ’.

The key relay system:
Each keyboard (manual) can play/operate a number of registers (sets of pipes).
It is impossible to place as many contact springs on blocks (BL) under the keys of the keyboard as there are registers.
If the organ is very small, having for example only four registers, that could be possible. A minimum of five contact springs would then be required, one for the positive contact which can then be switched through to the four registers. Therefore a system is required which will multiply the contact made by the key by the number of registers.
That system is the key relay.

Technique behind the Theatre Organ part 9



This article describes part of the electro-pneumatic relay.
More can be learned when visiting concerts in Dordrecht as this type of relay is set up in the cantine.