NR NR/SIN/083 ISSUE 2 PDF

This Special Inspection Notice applies to four types of fibre-optic position light signal, all manufactured by Signal House Ltd prior to May 2003. These may be in use as shunting signals, subsidiary signals or Limit of Shunt indicators.

Purpose

Fibre-optic position light signals manufactured by Signal House Ltd have been found to suffer from ‘phantom' indications in some ambient lighting conditions. The effect is caused by the front screen. It seems to be more noticeable after the signals have been in service for some time.

This Special Inspection Notice defines the types of affected signals and the action to be taken to replace the front screens with alternative materials not producing such serious effects.