The recommendations below are for more "normal" usage.
We recommend wiring the standard level COS-11 in a 2 wire configuration with a 1k resistor in series with the white wire (source wire) to ground. This reduces the output of the standard mic by 6 dB which will prevent overload of the input buffer on the UM400. This isn't necessary for the SM series since it cannot be overloaded by the COS-11 under any circumstances. It does make the microphone compatible with both transmitter series.
The Red Dot Cos-11's are designed to have 9 to 10 dB less output than the standard COS-11's and can therefore be wired with the source lead directly to ground.
Adding a 1k resistor to the source lead of either microphone will drop the 2 wire output by 6 dB compared to the source being wired directly to ground.
Using a 3k source resistor will drop the output of either mic an additonal 6dB compared to using the 1k resistor or 12 dB total. This much gain reduction should not be necessary and is for information only.
We also recommend wiring our pin 2 to pin 4 to make the wiring fully compatible with our UM400 and older Lectro transmitters. A schematic is below.