This pocket sized light detector has a key chain ring on the bottom of it.
To the left of the key ring is the power switch.
You switch the device on by pressing this switch away from the key ring.
The light sensor is on the opposite end of the key ring.
The front of the device has a single button.
To use, switch the device on and press and hold the button while pointing the light sensor towards the light you're attempting to detect. As the intensity of the light increases, the pitch of the light detector increases. As the intensity of the light decreases, the pitch of the light detector decreases.