Here's the remote hard drive selector connected to the power supply and two Western Digital ATA hard drives. The motherboard is an Asus A7S266-VM/U2.
Hard drive 1 boots Ubuntu Linux.
Hard drive 2 boots another operating system.
Both these drives are seen by my bios as a Master Drive.
On the next 2 pages, I'll show you how to make the remote selector switch.
Before touching any electronic circuit boards, read the warning on Page 2.