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4.5 Internet Linking
IRLP sends receiver audio to a sound card - which converts it into ADPCM digital data. The Linux PC then converts this data into digital packets with IP addresses for the destination node and sends them over the internet to a destination Linux PC decodes and sends them to the sound card and out to the transmitter microphone of the link radio which then transmits the audio out over the local repeater. The transmitter is keyed as soon as these TCP/IP (Internet Protocol) packets start to arrive. When the data stops the link radio reverses the process automatically.
PGP keys are assigned to each node to establish security. When a connect request is made the connecting node exchange key challenges which must be correct or the connection is refused.
IRLP, unlike EchoLink, does require the use of a radio.
Much more information here:
If you can reach an FM repeater or simplex station equipped that has been set up with EchoLink, you can use DTMF commands from your radio to access the EchoLink network. If you are a licensed amateur with an Internet-connected PC, you can access EchoLink stations directly from your PC.
EchoLink is very much the same as other existing VoIP applications except that it permits a direct link to an amateur radio station's transceiver. Prospective users must have valid callsigns to be use EchoLink.
Felt by many to be a watering-down of ham radio because one may make contacts worldwide without a radio ever being involved, EchoLink is still a savior for many licensed hams who, due to their circumstances, could not otherwise make contacts with any other amateur radio operators at all.
An example of how this works:
I fired up the software on my computer and EchoLink signed on for me, presenting me with a long list of active users. This list is broken down into Links, Repeaters and individual users. I noticed a repeater in the Great Falls, Montana area and accessed it just to see if anyone was there. I quickly made contact with another ham who was driving around in Great Falls, and we enjoyed a nice QSO for about 15 minutes. This gentleman could just as easily have been at his computer, as I was, rather than on a mobile two meter rig.
Feedback received on this FAQ entry:
It provides a full-featured radio digital message transfer system, worldwide. Email transfer with attachments, position reporting, graphic or text-based weather bulletins, and emergency communications are available to Amateur radio, the Military Affiliate Radio System (MARS), and UK Cadet Forces communities by linking radio to the Internet.