Yes, they can be installed.
On the echo board itself, you should have O/P and I/P screened onto the board. the white wire on the I/P side will solder to the mic jack on the radio. The O/P white wire will solder to the audio wire. You have to desolder the audio wire from the mic jack first, then connect the O/P white wire to the audio wire. The shields from the I/P and O/P wires can be soldered to a PCB ground source anywhere on the radio.
The power wires are pretty straight-forward. Observe polarity of course. Some boards have a brown wire for a ground wire, some are black. Red goes to a +8V source (some boards use +12V so observe that accordingly) and eithe brown or black will go to PCB ground.
Some boards have another set of connecters, labeled PTT I/P and O/P. Unsolder the PTT wire from the mic jack. Solder the PTT I/P wire to the mic jack, solder the O/P wire to the PTT wire you desoldered off the jack.
In most cases, you are done, and it should work. Double check your work and enjoy.
~Cheers~
