Both FAIRCHILD670 mkI and mkII are equipped with a Link that allows to gang the side-chain signals in 4 different modes :
1) LEFT/ RIGHT mode :
That is a normal Dual Mono mode, with two separate audio channels and two thresholds
Or
In LINK mode, with three possibilities :
2) Master Left + Slave Right, if you only use the Left Channel Threshold and keep the Right Channel Threshold down.
3) Master Right + Slave Left, if you only use the Right Channel Threshold and keep the Left Channel Threshold down.
4) Left + Right Masters (summed together), if you use both Threshold Controls at the same time.
