1235373 Autotrol Logix Electronic Control Optical Sensor Water Softener Parts. I acquired an entire lot of Autotrol new and used parts and will be listing more.
Optical Sensor, PN 1235373, used with Logix Electronic Metered Control (all use this part).And Autotrol 360, 368, and some Pentair (Fleck) = module,sensor,photo interrupter
It is used to "tell" the control board "where" the cam or camshaft has moved or advanced to, in the various cycles.
Failure (or just being dirty or wet) can cause Err 3 in many Logix controlled valves.
Also used in Fleck (Pentair) model 5800 series valves 5800 / 5810 / 5812