They replaced the Almex machines with Omniprinter that were used previously for on-board train ticket sales.
The PORTIS was the first British Railways ticket issuing system to use thermal roll ticket stock.
The production version of PORTIS was introduced in 1986 and a modified version which accepted credit-cards was introduced slightly later. This was known as SPORTIS (Super Portable Ticket Issuing System).
The SPORTIS memory was configured for each route that the machine would operate, so that it held the most likely fares that would be requested. If an unusual fare was requested, then the ticket inspector would have to refer to fares manuals and enter the details manually.
SPORTIS weighed around 2.9kg. The original specification stated that it should be about the same weight as two bags of sugar.