The CTR2-Mini Audio I/O module interfaces your radio to the CTR2-Mini Audio Controller. This controller allows you to share up to two microphones, a headset, a USB audio connection, and CAT control with all of your radios.

NOTE: The Audio I/O module is not directly compatible with CTR2-Mini or CTR2-Mini+. If you are not using the Audio controller to manage transmit and receive audio (i.e. just sharing CAT, PTT, and Key) use the CTR2-Mini Radio I/O module to interface the Mini to your radio.

How it works

The Audio I/O module adds Line-In (Rx audio) and Line-Out (Tx audio) to the control wiring and replaces the CTR2-Mini Radio I/O module when you want to manage audio in your CTR2-Mini system. Because of this, the Audio I/O module isn’t directly interchangeable with the CTR2-Mini Radio I/O module and cannot be plugged directly into the Mini.

The diagram below shows how the Audio Controller and Audio I/O modules are integrated into a CTR2-Mini system.

The Audio controller sits between the Mini and the I/O multiplexer (or manual RJ45 switch) and processes the audio from the Audio I/O module. It then sends the CAT, PTT, and Key signals on to the Mini. As far as the Mini knows, it’s connected to a normal Radio I/O module.

When the CTR2-Mini I/O Multiplexer is deployed as shown above you need to move a jumper on that unit so it monitors the correct data line. Details on this on in the CTR2-Mini I/O Multiplexer manual.


The Audio I/O module is simple to set up.

First, determine which CAT signal polarity you need for your radio and strap J1 accordingly. There are three options available:

  • Normal TTL – used on most Yaesu radio (unless they have RS232 CAT ports like the FTdx101), Xiegu, and some Kenwood radios.
  • Inverted TTL – used when the radio has an RS232 CAT port.
  • CI-V – used for Icom radios that use the CI-V CAT interface. Sorry, the IC-705 doesn’t have a CI-V port.

Next, determine if you are going to use speaker audio or Line-Out on the radio. If using speaker audio and plugging into it will mute the speaker, install a jumper on JP1 to terminate the speaker output of the radio in 10 ohms.


The CAT I/O and PTT/KEY OUT jacks on the Analog I/O use the same pin out as the Radio I/O module so the radio cables on this page can be used.

The AUDIO I/O jack has Line-In on the TIP (receiver’s Line-Out or speaker) and Line-Out on the RING (transmitter’s Line-In or microphone). A 1/8″ stereo plug to dual-mono plug cable can be used to bring these signals out. If you use this cable, cut the white and red mono jacks off and install 1/8″ stereo jacks in their place. Use a piece of heat shrink to make each cable – the white plug goes to the TIP of the stereo plug and the red plug goes to the RING of the stereo plug. This needs to be done otherwise the RING terminal on the plug will short to ground when you plug the mono plug into your radio.