Based on ETI project 514. Triggers a flash gun using an SCR, when sound level received by an electret microphone exceeds a certain level. This sound level is adjustable. The delay between the sound being received and operation of the flash is adjustable between 5 and 200 milliseconds. A red LED lights up every time the sound is loud enough to trigger the flash. This is handy when setting the unit up to suit the scene, without waiting for the flash unit to recharge or flatten its batteries in the process. This kit allows you take interesting pictures such as a light bulb breaking. PCB: 62 x 40mm.