The A-166 is a multiple logic module with 3 inputs for each of the two identical logic modules. The logic module produces an output for the logic states of AND, OR and EXOR.
There are also 2 inverters as well which allows further functions for NAND, NOR and NEXOR.
The input sockets are normalised so the same functionality will work with 2 inputs rather than the need to have always 3 inputs.