DOEPFER A-110-1 Voltage Controlled Oscillator

The DOEPFER Module A-110-1 is a voltage-controlled oscillator. This VCO's frequency range is about eight octaves (ca. 15Hz ... 8kHz). It can produce four waveforms simultaneously: rectangle, sawtooth, triangle, and sine wave. The output levels are typically 8Vpp for saw and rectangle, and 10Vpp for triangle and sine. The frequency or pitch of the VCO is determined by the position of the octave (Range) switch and tuning (Tune) knob, and by the voltage present at the CV inputs. Frequency modulation (FM) of the VCO is therefore a possibility. Footage (the octave of the fundamental) is set by the Range control in five steps, and Fine tuning controlled by the Tune knob. The tune knob range is about +/-1 semitone for older modules. Since about middle of 2015 the value has been increased to about+/- 1/2 octave. In the A-110 service manual  is described how to modify the range.
You can control the pulse width of the square wave either by hand, or by voltage control - Pulse Width Modulation or PWM.