Product Description
A signal box lamp indicator bell, these bells were used where signal oil lamps were repeated in the signalbox to show they were lit. In the event of a lamp going out a special expander unit contacts contained within the lamp case was heated by the oil lamp burning and completed a circuit, if the lamp went out the bi-metallic strip in the expander would cool down and contract thus breaking the circuit. The relay would drop in the box and the indicator would show lamp out and the bell would ring to alert the signalman. This example is in tested working order and is fitted with 2 early Ivorine plates.
