In the early stages of the run up to the final legislation, most of the pro-CB lobby wanted the government to legislate around the US standard CB system, primarily due to the large user base that already existed. The UK government made it clear from the outset that legislation for use of this equipment would be unlikely. Interference problems associated with badly calibrated amplitude modulated (AM) or Single Side Band (SSB) equipment were cited as the main factor, and it was made clear that if any system was legalised it would be frequency modulated (FM). The CB lobby argued that interference from AM was unlikely to occur from the use of original unmodified AM radio equipment, a view initially rejected but later accepted by the Ministry of Defence.