Sorry, no schematic. I originally designed this and use it in my computers as a PWM booster/ signal cleaner, as it does output a nice clean/ powerful pwm copy of the pwm you choose to input. I had multiple issues with fans not responding correctly to motherboard/ corsair/ noctua/ etc. signals when I would try to combine multiple ones on a hub, so I decided that the best fix would be to make sure that the PWM signal was been transmitted "clean" and as strong as possible. It ended up working better than I could imagine. Yes, you could use a 555 instead, but you'd end up with an inverted signal which is why the 556 timer was the perfect solution. It simply takes a 5v line, pwm signal, and ground and outputs a steady 5v PWM exactly matching the input, but without the current limitations as most PWM signals are spread pretty thin. This little module solved all of my fan and pump problems. What's great is that I realized that it could be used in multiple untold applications as it can copy almost any signal and send it out "fresh" and "powerful". I didn't add any holes as I made this PCB myself with the old toner transfer method, but I plan on getting some extra modules made. These are perfect if you plan on using a fan hub of 4 or more. I tied the PWM to the 5v output w/ an 820-870 ohm resistor specifically for Noctua PWM matching so that at the lowest PWM ON setting, the fans are still running . You may utilize a 10-100uf capacitor to help clean up the 5v line. These are in all my computers now. The PWM signal produced is a direct copy and much cleaner than the original produced by the Noctua standalone PWM. It also works great connected directly to my ASUS motherboard as well as use with other splitters.