Module A-132-4 contains four identical voltage controlled amplifiers (VCA) with exponential control scales. 

Each VCA has two control voltage inputs (C1, C2), a signal input (In) and a signal output (Out). 

The control voltage inputs C1 and the signal inputs can be normalled by means of internal jumpers, 
i.e. the corresponding input signals of unit #1 can be connected to the switching contacts of unit #2. 
Those of unit #2 can be normalled to unit #3 and those of unit #3 to unit #4. 

If the normalling is not desired the jumpers have to be removed. 

In addition the sum of all four outputs is available (bottom left socket with the sum sign). 
Therefore unit #4 has only one control voltage input (only C1, no C2). 
If desired this socket can be jumpered as control voltage input 2. 
But then the sum signal is no longer available as a socket (only as an internal pin). 

For each VCA output a jumper is available that determines if the output signal of the corresponding VCA is added to the sum signal. 

From the factory all four jumpers are set (i.e. all four VCA output signals are added). 

By removing of one or more of the jumpers one can choose which VCA output is added to the sum. 
The jumpers can be replaced by switches too.

technical details

Width: 6HP 

Connections - units 1-3: 
C1 input 
C2 input 
Input (signal/audio) 
Output (signal/Audio) 

Connections - unit 4: 
C1 input 
Input (signal/audio) 
Output (signal/audio) 
S-output (sum)