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Barcelona had trolleybuses for a rather short time, between 1941 and 1968. The first line was actually quite an impressive feat: It was designed in record time and with very limited resources due to the ongoing war. Old bus chassis from the 1920's were rebuilt into trolleybuses with mostly spare tram parts. The whole line plus its vehicles were designed, built, tested and put into service in just over two years.
Pic related was taken in 1956 and shows one of these original trolleybuses.
As a fun fact, in those days trolleybuses in Spain weren't called "trolebús" as is usual in spanish, but "filobús", which is taken from the Italian word for trolleybus. Probably because fascist Italy assisted Spain on the technology.