This is Coin Acceptor Sensor 

Step 1: Connection

Red:+DC12V
White: Signal output

Black: GND
Gray: Counter-optional

Step  2: Put on a Sample Coin in (4)

Step 3:

Switch for Normal Close or Normal open mode see the switch on  (2)

Step 4:

Switch and VR tuning for tolerance of coin acceptance see (5) and (7)

Step 5:

Switch for Pulse duration with the switch located at (6)

• Long duration of Pulse: 100ms
• Common duration of Pulse: 50ms
• Short duration of Pulse: 30ms