The CO2 has a three-position slide switch that selects its operating
mode.
In the first position ("optical -> coax") the CO2 has a single data
path: it takes an optical input signal and passes it through to both the
optical and coaxial output jacks.
In the second position ("bi-directional"), the CO2 has two data paths:
the optical input is connected to the coaxial output, and the coaxial
input is connected to the optical output. In this configuration the CO2
duplicates the function of the Fostex COP-1.
In the third position ("coax -> optical"), the CO2 has a single data
path: it takes a coaxial input signal and passes it though to both the
optical and coaxial output jacks.
Next 
