The TSX50 is an integrated communications system which uses an innovative modular design. Up to 10 peripheral circuit cards can be plugged in or taken out without upsetting the system. This allows easy system expansion, fault finding and card replacement. The TSX50 is a compact digital electronic system using stored program control and advanced digital architecture.

The TSX 50 can simultaneously use tone, pulse dial or TX14 feature phones. It can cater for up to 160 extensions, 32 exchange lines (trunks), 24 private circuits and has its own console. It has features such as call information logging, automatic route selection, extension metering, direct inward access, direct outward dialling, emergency switching, pick-up groups, baby monitoring, and remote access.

The TSX50 was first launched in June 1986 with the version UK1 which had G3543/02 software. In July 1989 the UK2 version was released with G3543/03 software. The final version UK3 was released in April 1990 with G3546/01 software. See the table below which explains the differences. The TSX50 had two types of power supply. Earlier versions had the 1A power supply fitted which had an output of 140W, whilst later versions had the higher rated 2A with an output of 225W. See below for the maximum capacity for each type.

The Meridian Norstar M8X24 modular Telephone System was designed to meet the high growth potential of small and medium sized businesses. The basic Meridian 8X24 Telephone System offers eight trunks and sixteen digital extensions. This can easily be expanded by the addition of simple self contained add-on trunk and extension modules. Any combination of six modules can be added to the Meridian Norstar 824 Telephone System to a combined maximum total of 128 ports.

An expansion card is required to add modules to the Meridian Norstar 824 Telephone System. Expansion cards are available as either a 2 module expansion card or a 6 module expansion card. The expansion card plugs directly into the Meridian Norstar 824 Telephone System. The trunk and extension modules then connect to the expansion card via a single plug in fibre optic cable.

Extension module M0X16 provides for the addition of 16 digital extension ports for system telephones. Extension module M0X8A provides for the addition of 8 analogue extension ports, a second unit can be added to the first to provide 16 ports. The M12X0 trunk (line) module provides for up to a further 12 trunk ports. The trunk module contains three slots to plug in 4X0 trunk cards, each trunk card provides four trunks (lines).

Meridian system telephones are plugged into a secondary LJU wired to pins 3 & 4 (blue/white & white/blue).