Detail:

red wire for 5V+, black wire commonly for 5V- and Yellow wire for TTL +. If you only connect its black wire and red wire, the laser would not work, you also need to connect its yellow wire (TTL+) to 5v+. When the TTL signal is connected, the higher the frequency is , the less brighteness the laser will have. when it is >15KHZ, the laser cannot be seen.

Package:

1pc 650nm 10mW 5V 12x40mm Red Laser DOT Diode Module