They can be individually changed without re-wiring the whole assembly. All units are 1 module wide unless otherwise stated. Voltage rating 240V a.c. 50Hz.

Dimensions:
Switch Module 25 mm wide x 59 mm high and 25 mm deep
Buzzer Unit 25 mm wide x 59 mm high and 34 mm deep
Single Dimmer Module are 25 mm wide x 59 mm high and 58 mm deep
Double Dimmer Module are 50 mm wide x 59 mm x 60 mm deep
24/240V Buzzer Unit 25 mm wide x 59 mm high x 31.5 mm deep
Cord Unit 25 mm wide x 59 mm high x 42 mm deep

For the dimmer (RS 292-8809 MK ) the power / load ratings are: Min. W or VA = 60; Max. W or VA = 320 and it uses 2 module widths in a standard MK Grid Plus grid.