A-174-2 is a modulation wheel module with two wheels.
The factory setting is a spring loaded wheel at the left side with bipolar voltage output (i.e. 0V in center position, positive voltage in the upper range, negative voltage in the lower range, voltage range about -5.5 V ... 0V ... +5.5 V) and a wheel without spring at the right side with positive voltage output (i.e. 0V in the lowest position and positive voltage when operated, voltage range about 0...+8 V). For the spring loaded wheel a voltage "plateau" around 0 V is preset (jumper) so that the output voltage is 0 V in a small area near the center position. By means of jumpers the factory settings can be changed.
For each wheel two jumpers are available: one for the voltage range (positive or bipolar) and one for the voltage plateau around 0 V. If these settings are changed even the wheels have to be re-adjusted mechanically. Therefore such modifications should be carried out by a qualified person only.