2003-2009 Zt-2 Wideband has a Non Linear Wideband Output (white wire). See graph below

2006-2009 Zt-2 Wideband has two wideband outputs. The Linear Wideband Output and the Nonlinear Wideband Output, which follows a natural output curve of Bosch LSU wideband O2 sensor.
The Zt-2 Linear Wideband Output is shared with the Narrowband Output (the Zt-2 purple wire). Typically the engine management systems use only a narrowband or a wideband O2 feedback.

2010 Zt-2 Wideband has one Linear Wideband Output (white wire)

2010 Zt-3 Wideband has one Linear Wideband Output (white wire) which is a configurable output.  The default output matches the Zt-2 2010 output and the Zeitronix Data Logger software may be used to configure the output AFR voltages to match 3rd party engine management systems or gauges.

Zt-2 Linear Wideband Output transfer function is: AFR= 2 * V + 9.6
For Use with 3rd party systems enter values as follows: 0 Volts = 9.6 AFR, 5.0 volts = 19.6 AFR

Dual Wideband AFR is possible using the linear wideband output. Two Zeitronix wideband units can be linked together by connecting the linear wideband output of a second wideband controller to the "User2" input of a Zt-2. The dual bank air/fuel ratio can be displayed on an LCD, Gauge or software and logged on a Black Box Data Logger. Additional dual channel air/fuel ratio configurations are available.
 

2006-2009 Zt-2 Wideband
The Zt-2s purchased after September 1 2006 are equipped with the Linear Wideband Output. To set up the Linear Wideband Output please open the ZDL software V 2.0.8 or later and chose the 0-5V Linear Wideband Output from the Settings/Narrowband Output Pin menu. The Zt-2 purple wire becomes the Linear Wideband Output.

2003-2009 Zt-2 Wideband
These Zt-2 Widebands are equipped with the Nonlinear Wideband Output (the Zt-2 white wire). This output follows a natural curve of Bosch LSU wideband O2 sensor.