i need help with a timer that i use with a sensor. i just need to know what type of sensor it is. it is wired to the button on the timer and i use 2 reflectors to start it at point a and stop it at point b. it's the same button used to start the timer and stop it. so it's like somewhat of a switch. can anyone tell me what kind of a sensor this is and where i could find one? any help would be great.