The "privacy tones" or "privacy codes" (as Moto calls them now) is a silent signal that is broadcast everytime the FRS/GMRS is transmitting.

Only if the receiving radio is set to use the same channel and privacy code - OR set to privacy code '0' (not using any privacy code), will you hear the transmission. Radios set to privacy code '0' will turn on for all transmissions on the selected channel.

If the receiving radio is on a different channel, you will not hear the transmission.

If the receiving radio is on the same channel, but using a different privacy code, you will not hear the transmission.

The thing to keep in mind is that regardless of the privacy code use, all radios using channel X (whichever you're using) use that same channel to broadcast. So, if two nearby groups are using the same channel, they are all transmitting using the same frequency. It is to get cross-talk on the frequency - two people transmitting on the same channel at the same time. In that case one of the groups should agree to move to an unused channel to avoid the cross-talk.

I don't think Motorola makes any pure FRS radios anymore. I think they are all FRS/GMRS hybrids. I've read lots of debate about whether people in the U.S. are allowed to transmit on the GMRS frequencies using those radios (since they usually transmit at higher Wattage). I've never heard a final answer on that. I got my GMRS license and simply don't worry about it.

Because antenna height has so much to do with the transmission range, I know of some people who use external antennas and hoist them up into nearby trees. Of course that's tough to do if you're wandering around the forest.

Someday I figure they'll come out with a relatively low-cost SPOT-like product that uses satellites to broadcast/receive text messages. Put that into a GPS and you have a nifty product. Now that would be cool.