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1997 — Psion Series 5 handheld
Psion introduced the Series 5 PDA to replace its Series 3 model. The new Psion 5 included an innovative sliding keyboard that came forward to provide stability when the clamshell was opened.
The Series 5 used the ARM710 processor that could run 10 to 20 hours on two AA batteries. It had a touchscreen and dual serial connectors (RS-232 and IR) for connectivity to other Series 5 devices.
Most significantly, the Series 5 ran the EPOC operating system, now known as Symbian. Largely through the efforts by Nokia, Symbian came to be one of the most-used OSes in phones of all times.