In amature radio, users can use what is called a phone patch to enable them to use a phone to establish connection to another party or user.
Phones are usually two wire and dont lend themselves to easy connection to the both the receiver and the transmitter so a hub is required.
I believe this curcuit bellow is the hub, the input connects to the receiver and the output to the transmitter.
However their is an issue with using this curcuit.
- Their is no curcuit protection that keeps oncoming received voice from hitting the transmitter and echoing back out.
I am looking for a better explanation on how this curcuit can work in feild radio and in facilitating a 2 to 4 atachment and how it can be used to inter connecting the required componets in amature radio.
This has been taken from my refrence data for radio engineering.