Analog summer module for Analog Paradigm Model-1 computer.
The module SUM8 contains eight summers which are grouped into two groups of four summers each. The four summers at the bottom each have three inputs weighed with 1, and two inputs weighed with 10. In addition to that the summing junction is also available. This is useful either to extend the input capabilities by additional resistive input networks (XIR-module, see below), or for additional feedback elements like diodes to limit the output value etc.
The four summers in the top row can be configured as so-called "free amplifiers" by disabling their internal feedback path. This is done by patching the FB jack to a ground jack. Such free amplifiers are used to implement implicitly defined functions like a division or square root based on a multiplier in the feedback path.
See also the INT8 module.