Electro-pneumatic stop actions utilise air under pressure to move the stop-keys, under the control of the thumb and toe pistons and either a setter-board or an electronic system to act as a memory system.
Electro-pneumatic stop-key actions contain the following:
• A stopkey mounted on a pivot wire with a bias spring.
• A pair of contacts which are made when the stopkey is in the ‘on’ position.
• A pair of pneumatic motors to move the stopkey ‘on’ or ‘off’.
• A pneumatic action with chest magnets to supply the ‘on’ and ‘off’ pneumatic motors. The chest magnets are controlled by the combination memory.
Electro-pneumatic consoles are relatively complex, but reliable and prompt in operation if properly maintained.