I bought a new pair of Motorola Talkabout FV300 radios and it simply does not work with them.  When I plug it in, turn it on and press the PTT button, the radio starts transmitting and doesn't stop until I shut the radio off.  I knew the VOX feature wouldn't work, but it was my understanding that it was supposed to still work with manual operation of the PTT button.  It does not.  However, it does work with my older Talkabout which is a T5000, but not with VOX.  I'm giving it two stars because they should have been more clear as to which radios work and which don't.