I want to use an empeg tuner to read voltages from steering wheel radio controls. Here's my problem. The Saab steering wheel has resistor circuits that are read by the SID (computer/display in the dash). The SID has a similar set up as the ADC circuit in the tune (5v with pullup resistor: reads voltage between 0 and 5 volts from steering wheel controls. I want to safely tap into this circuit to send these voltages to the tuner. This means I don't want to ALSO send the 5 volts from the tuner thru the circuit. I don't want to completely disconnect the SID wire because it also turns on the horn. Can I safely intergate the tuner ADC into this circuit using resistors, diodes or other? In other words how would I attach a second tuner ADC circuit to one already working without frying the first?