PACTOR is a new form of data transmission that combines two prior methods called packet radio and AMTOR, a form of radio teletype messaging. PACTOR enables wireless transmissions and uses a frequency shift keying (FSK) method. Various updated versions of PACTOR include PACTOR-I, PACTOR-II and the newest version, PACTOR-III.
PACTOR is used by some amateur radio bulletin boards. It is also commonly used for transferring data, including email, from marine stations.
Techopedia explains PACTOR
As a form of AMTOR, PACTOR evolved from an original radio teletype technology that simulated an electromechanical teletype for wireless transmission. AMTOR also added error correction for signals, including automatic repeat request (ARQ) and other error-handling abilities. PACTOR improves on error handling for transmissions, creating better messaging across long distances, and achieves a higher data transfer rate of up to 200 characters per second.