In reply to dave_59:
The real-valued output is the value of voltage applied to one of the tank ports. The other port is driven with the complementary voltage. That is, the two tank ports are driven with either 3V, 0V or 0V, 3V on the two ports. The z value will model the case when the tank is disconnected from any voltage, and responds with a decaying sine wave until it fully discharges.
I know about the (V,I,R) triad, and will use that method if no other method can be identified. But it seems like more work than needed. For example, can I just use a force to z when I want to tristate the ports?