Originally developed for switching shop-window display or street lighting on an automatic program. Similar clocks had earlier been used for controlling gas lamps by turning a gas cock instead of opening and closing electrical contacts. The use of time-switch clocks was greatly extended during the Second World War, when they were used for time-delay bombs, mines, etc. Nowadays they are incorporated in many devices for control of domestic heating, cooking ovens, lighting for intruder deterrence, process control, etc. An English firm, Horstmannn of Bath, have pioneered much of the work in this field. Later developments include the programme clock which will carry out switching duties on a weekly basis, suppressing operations at weekends if required. Many millions of these clocks are in daily use throughout the world; the majority are electrically driven, spring reserve being fitted where a break in supply might result in disastrous disruption to the program.