The test probe has two different ends in order to test different water activated lifejacket lights.
How to test your lights:
1. Insert the plug into the water contact socket of your light. The light should flash within 2 minutes.
2. When the light flashes, remove the plug. The light should continue flashing.
3. If the light does not flash, it must be replaced.
4. To turn off the light, press and hold the manual switch for 1 second.