The Psion Series 3 range was regarded in 2009 by writer Charles Stross as an unsurpassed PDA[1] because of its long battery life (20 to 35 hours), its stable and versatile software, and its durable hardware.

All have a DC input socket for optional external power-supply via a mains transformer AC adapter.

The Series 3's innovative clamshell design did have some problems: breakages of any of the four hinges; loss of function in the button bar between the two halves of the clam; and deterioration of the cable linking the keyboard half to the screen, leading to a serious display problem with vertical lines appearing.

Psion, Acorn and third party software was available loaded onto such memory cards which were available as separate packs.

The tone dialing feature was integrated into the Psion's Agenda, Contacts and Data applications.

Besides the agenda with multiple views, it featured a database, a word processor, a spreadsheet with charts, world times, and more.

With an optional modem, it could connect to the Internet for very basic web browsing and email functionality through the official Psi Mail app.

Essentially a renamed OEM version of the Series 3 with slightly different on-board software, the Acorn Pocket Book was marketed by Acorn Computers as a low cost computer for schoolchildren, rather than as an executive tool.

Other programs were renamed: System became Desktop, Word became Write, Sheet became Abacus and Data became Cards.

[8] The Series 3a has a NEC V30H CPU (running at 7.68 MHz and thereby twice as fast as the Series 3), a microphone for voice recording, an input/output (I/O) port (for modem, printing and PC synchronization), and 256 kB, 512 kB, 1 MB or 2 MB of random-access memory (RAM).

The increased power consumption of the faster processor and larger screen was mitigated by using a lower-voltage version of the V30H, leaving the stated battery life unchanged at 80 hours.

[10] This added back some of the applications omitted from the original Pocket Book, so was closer in specification to the standard Psion model.

A user has one try: if mistyped, the System Screen must be killed and restarted by typing Ctrl+Psion+⇧ Shift+K before a retry can work.

The ability to browse the World Wide Web on the device was also available through the STNC HitchHiker mobile browser,[12] although it was only available for use with an external modem.

A Mob-i-Mail software package was used to enable sending email via Short Message Service (SMS) and Mobitex networks.

The flash modules did have the limit of needing to be re-formatted entirely to reclaim space from deleted or modified files; old versions of files which were deleted or modified continued to take up space until the module was formatted.

"[14] PCMag's Jonathan Matzkin said "With an improved keyboard and a more adjustable screen, the Series 3 would clearly be the new leader in the palmtop field.