Quantity   Component name
1 × Battery backup unit Can be any size. Obviously the bigger it is, the more stuff you can fit in the case!
1 × Brain I used a Raspberry Pi 2 B that I had laying around.
1 × Connectors or test leads (Optional) To attach the LED and switch to the GPIO on the Pi.
2 × Ethernet cable Need to be fairly short and flexible.
2 × RJ45 ethernet jack (Optional) I used a couple of solder-on jacks from another BBU, to keep the stock look.
1 × USB A to micro USB cable To power the Pi.
1 × USB A to barrel cable To power the switch. This can be made.
1 × M3 screws & nuts (Optional) To make things removable.
1 × Network switch Mine had five ports and was only 100Mb/s, but the ports on a BBU are rarely gigabit anyway.
1 × Power adapter for the Pi I used a very slim 5V 2A wall wart with USB output.
1 × Power adapter for the switch My switch took 5V 800mA, so I used a second slim 5V 2A wall wart.
1 × Momentary push button One that's only engaged while being pressed.
1 × 270ish ohm resistor
1 × 10k-100k ohm resistor
1 × Wire Multiple lengths, gauges, and colors