From the manual...
The KE72 Mouse Button Inputs:
Use this port to connect switches for simulating mouse button information.
These inputs are activated by shorting them to the common Ground signal
provided. All input signals must be compatible with 5V logic levels.
Connector on KE72-T FOR MODEL KE72-T ONLY!
__________
|
|---- Right Mouse Button Input
|
|---- Middle Mouse Button Input
|
|---- Left Mouse Button Input
|
|---- Logic Ground
__________|