The LaserJet 4 was HP's first 600 dot per inch laser printer. It was based on the Canon EX engine and had a maximum print speed of eight pages per minute. The LaserJet came standard with a 100-sheet multipurpose "lip" tray and a 250-sheet main input tray which sat under the machine. The construction of the multipurpose tray was somewhat "tinny" compared to previous lasers, but it was reliable. An optional 500-sheet input tray was also available. For the first time, the LaserJet 4 could also listen on both its serial and parallel interfaces at the same time. It included an interface slot for optional MIO LAN cards. The Postscript/Mac connect version of the LaserJet 4 was the LaserJet 4M, also introduced in 1992.