EQSO is a client - server program, which was developed by radio amateurs. It allows radio stations to each other, to communicate with wireless gateways and repeaters via the Internet using speech. In this case, a voice- over IP protocol is used. This principle is also called Radio over IP. The name eQSO derived from the Q- key " QSO ", which is used in amateur radio and CB radio operators as an abbreviation for " radio talk ", and the prefix " e", which is "electronic" for, from.

EQSO is also used in free radio ( CB Radio, PMR446, SRD and Freenet ). Here, the PC users log on to a client software on the server, while the other radio services use so-called gateways. The gateway establishes a connection between the server and the radio partner by enabling voice radio divided into digital packets and these are transmitted to the connected computer. The gateway computer then transmits the data packets transmitted over the Internet to the server which converts the packets back into voice. So it is possible that CB Radio, PMR, LPD and Freenet users can chat together with the PC users over thousands of kilometers.

For these unlicensed radio applications specially a PMR radio version was programmed and updated several times. Alternatively, the derived program eQSO Free Radio Network ( FRN ) was developed. Both programs are now used quite frequently and are for server operators (server software), PC users ( client software), gateway operators ( gateway software ) and HF - users ( those who connect their radio to the gateway ) equally popular.