I have a telephone switch that is plugged into a serial port. This switch is very simple: it has 3 telephone plugs, one for the phone line, one for phone 1 and one for phone 2. It also has a serial port and a power cable. By sending info on this serial port, the switch changes from phone 1 to phone 2. It only allows one phone to use the line at a time.
The problem is that I dont know what info I must send into the serial port to make it switch the phone lines. There are only 2 wires connected to the serial cable:
x x o o o
o o o o
The x's are the connected wires (pins 4 and 5 I guess).
Any ideas on how to make this device work? I work with delphi on windows xp.