microtech and tacho problem

[Hyuga]

Can anyone tell me how to hook up the tacho with microtech ecu? I found that my tacho is for positive current while my microtech only supply negative current for the tacho so when they connected up, the tacho doesn't read. Any idea?

[Hyuga]

I searched on Toymods and found this, don't know if its what I want.

also would like to know if a afterarket tacho can be connected with the microtech tacho wire with no further modification on the circuit?