The PL tone may still be required to access the phone patch. Alternatively, the communications specialist or other member of the command staff is usually willing to make an emergency telephone call for you from base camp if necessary. If you are interested in accessing a repeater's phone patch, you will also need a DTMF keypad on your radio. A radio capable of storing several operating frequencies is a good idea. You can then change from one frequency to another by simply turning a knob or pressing a button.
Opinions vary on how many channels are necessary.
The communications specialist at base camp may use several more. Some people find it convenient to program their radio with a larger number of SAR and repeater frequencies and then not have to program their radio as often. This is a matter of personal preference. If you have a field programmable radio and are comfortable doing so, you can buy a radio with fewer channels. A few additional pointers follow, acquired from mission experience.