This interface is used to create dedicated two-wire links for analog signals such as voice, FSK or DPSK. Once the communication channel with the remote card is setup, each of the four ports connects to the corresponding port on the remote card, and the link is always active. There are no DC or ringing voltages on the output.
We're very happy with the multiplexers that you supplied. The nature of the customer’s installation means that we won’t hear general feedback unless things go wrong – we’ve not received any complaints so assume that there have not been any problems. We found the equipment straight forward to set up using the supplied documentation.