The A-176 provides three voltage sources, to use wherever an extra CV is required. The top two voltage sources (CV1 and CV2) have controls for coarse and fine control of the voltage output; the third source (CV3) just has the one control. The range of the voltages output can be preset either to 0 to +5V or to -2.5V to +2.5V depending on your likely requirements, there is a jumper on the circuit board for each of the three voltage sources.
A typical use for the module would be to provide fine as well as coarse tuning for an A-110 standard VCO (which unlike the A-111 only has one tune control).
In general, this module will be useful whenever you need a manually controllable CV on a module which does not itself have a built in control.