Elkay 400A Columbus 1G Pneumatic Time Delay Push Switch. 
 
The Columbus® pneumatic timer is an easy to fit and cost effective way of automatically turning lighting off after a set period of time. Pushing the button switches the contacts and activates the time delay, which can be set at installation anywhere between 5 seconds and 5 minutes (Note timings are approximate).
 
Specification:
Single Contacts
Resistive/ Incandescent (e.g. Filament Lamps) 6A 1380W
Fluorescent/ Compact Fluorescent (6 fittings max) 3A 690W
Externally ballasted LED 3A 690W
Internally ballasted LED 100W
Suitable for use with 16 mm or 25 mm BS back box
Available in white finish
No neutral required
Replaces existing single gang wall switch
5 seconds to 5 minutes adjustable activation
With screw cover caps for aesthetic look and security