Transformer 230v/50hz to 12v AC used with many Autotrol ( GE Osmonics ) valves. This is the "C" outlet and voltage.
Required for 440i low voltage and 460i, 740, 760 electronic timers ( and a few other timers ).
Plugs into a small jack located on the Timer

NOTE: Type C plugs can also be used with E and F and some L receptacles. This type of plug is very common in most "universal" adaptor sets. (Though the diagram shows a circular plug, quite often Type C plugs have a rectangular form factor, as in the photo above.)

Where found:

Albania, Algeria, Angola, Argentina, Austria, Azores, Balearic Islands, Bangladesh, Belgium, Bolivia, Bosnia, Brazil, Bulgaria, Burkina Faso, Burundi, Cameroon, Canary Islands, Cape Verde, Central African Republic, Channel Islands, Chile, Comoros, Congo, Croatia, Dem. Rep. of Congo (Zaire), Cote d'Ivoire (Ivory Coast), Cyrpus, Denmark, Djibouti, Egypt, El Salvador, Equatorial Guinea, Eritrea, Faeroe Islands, Finland, French Guiana, Gabon, Germany, Gibraltar, Greece, Greenland, Guadeloupe, Guinea, Guinea-Bissau, Hungary, Iceland, India, Indonesia, Iran, Iraq, Isle of Man, Israel, Italy, Kazakhstan, Korea, Kuwait, Laos, Lebanon, Lithuania, Luxembourg, Macedonia, Madagascar, Madeira, Mali, Martinique, Mauritania, Mauritius, Monaco, Montenegro, Morocco, Mozambique, Myanmar, Nepal, Netherlands, Niger, Norway, Oman, Pakistan, Paraguay, Peru, Philippines, Poland, Portugal, Romania, Russia, Rwanda, St. Vincent, Senegal, Serbia, Slovenia, Somalia, Spain, Sudan, Suriname, Sweden, Switzerland, Syria, Thailand, Togo, Tunisia, Turkey, Uruguay, Vietnam, Zambia.