Sangamo are a UK manufacturer of time clocks/heating controls, thermostats, immersion controllers & programmers. The brand is also recognised for their Round Pattern Time Switches.
S254.2 - 20A 3 Pin 24 Hour Round Time Switch Day Omit
The 24 hour programming time switch cycle performs the same sequence of switching operations on each day and can be quickly and easily set using the small manual levers on the dial. A “day omit” device allows you to select any number of days in the week on which the switching cycle can be disabled. A general purpose timeswitch for heating, ventilation and equipment control applications