1) Pretty much a phone with a full-duplex (i.e. tranmit on one
frequency and recieve on another, and it always transmitting and recieving) (radio), and that allows both people
on the line can yell at each other at the same time.
2) A device permantly attachted to a
teenybopper.
Whats great is, people think
cordless phones cannot be listened to, but sense it uses radio waves to be 'cordless', then anyone with a scanning reciever on the base (this is a duplex system, remember) can listen to BOTH sides of the conversation.
In my free time, i listen to my neighbor's cordless phone conversations on my
radioshack radio scanner.