The MK range of 7 day commercial and industrial controls includes On/Off units for boiler control, lighting, bell ringing and siren sounding applications, i.e. class change bell ringing in schools or for breaks and shift changes in factories. Programme entry is via a membrane keypad with audible feedback. For security it is only possible to enter or change the time, programme and extend the duration with the removable key in place and turned to the setting position. The On/Off units, 811 851 and 852 feature a programmable 0 – 8 hour extend or continuous override and a crop override to cancel the remainder of an on period. The Auto/Off rocker switches allow outputs to follow the programmed events or to be switched off. The pulsed units 841 and 842 feature programmable duration and pulse type, continuous or intermittent. The Auto/Off/Man rocker switches allow the outputs to follow the programmed events, to be switched off, or to be manually on while the switch is held down in this position.