There are many commercially manufactured sound card interfaces on the market (more...). Below are some basic circuits that may be utilized. In order to utilize the RoMac 10 Band Equalizer to it full potential (transmit & receive), the interface unit must raise the CTS line on the serial port on order to switch the equalizer to the receive mode. Check with the documentation for your interface. If the interface unit does not raise the CTS line while keying your radio, the full transmit and receive functions may be used by using the space bar on the computer to key your radio.

An inexpensive and fairly good isolation transformer is available at BuxComm.com model number XFMR115. This transformer has good low end frequency response down to 75 Hz at -6 dBv.