- DC & AC types standard supply voltages covered by 3 varieties
- 3 wired polarised or 2 wire bi-polar DC second stage control on all types.
- 3-wire AC second stage control on YO5, YL5 and YO3 types
- Complies with BS 5839-1 : 1980 Clause 9.5
- Choice of lens colour (except YO3)
- 32 sound signals
- 2 Stage Alarms
- Radial stackers.