Digital technology quickly replaced analogue systems at national and major regional switching centres and new international gateway switches were installed. The oldest electromechanical step-by-step exchanges and manual operator-manned local exchanges were the first to be converted to digital technology. More modern electromechanical crossbar exchanges, using Ericsson ARF, Hitachi and ITT Pentaconta technology dating from the 1960s and 1970s were converted to digital bit by bit through the late 1980s and early 1990s. These crossbar switches were capable of providing voice service that was comparable to digital switching technology.