Abstract: An optical rotary switch is used in combination with an optically activated relay for causing make before break contacts between paired sets of relays including photoemitting and photoreceiving portions. The rotary switch comprises a switch base with an assembly rotatably mounted thereon for optically coupling the paired sets of relays including photoreceiving and photoemitting portions of the switch. A first optical exciter port and a first optical indicator port constitute a first relay and are disposed on the base for communication of optical signals. A second optical exciter port and a second optical indicator port constitute a second relay are also disposed on the base, angularly separated from the first optical exciter and first indicator port by a preselected angular interval.

Abstract: An electrical switching system comprising a relay having a photoelectric element comprising a photodiode, with first and second electrodes and a photosensitive portion. The photosensitive portion is responsive to optical stimulation for electrically coupling the first and second electrodes, permitting transmission of electrical current between them whereby the relay can be connected to a source of electrical power. The electrical switching system comprises a pair of such relays which cooperate through optical signals to operate the switch system. Also a part of the switching system is an optical rotary switch for controlling the operation of the switch system. A further aspect of the disclosed invention comprises a nuclear power generating apparatus including a monitoring arrangement operated by the electrical switching system of this invention.