A packet cluster system allows radio operators or shortwave listeners to "spot" transmitting stations by submitting their call sign and frequency of operation to a computer system which redistributes the information to all other connected users of the system. The term "packet cluster" is derived from the use of AX.25 packet radio as the original connection mode to the computer systems; today, connections are commonly made by telnet over the Internet instead. Packet clusters are designed to help radio operators share information so that other stations can find transmitting stations that might be of interest to them.