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Comment by MichaelAza

2 years ago

Under Telephone History it says:

> The current PABX-based system went live over the weekend of 27-29th July 1990

A PBX serving a whole country, even a small one, is wild. From what I could find [1] the system used was a UXD5 exchange [2] which is technically a PSTN exchange intended for rural areas and based off the Monarch 120 PBX [3].

The architecture of the UXD5 is common to a lot of telephone exchanges of the time (possibly modern ones as well?) with actor based message passing, actors running on different levels (more real time vs less real time) and a combination of assembly and a high level language (in this case, Coral [4]). Fascinating stuff.

[1] https://techmonitor.ai/technology/cable_wireless_has_contrac...

[2] https://sites.google.com/site/monarchcallconnectsystem/uxd5-...

[3] https://sites.google.com/site/monarchcallconnectsystem/monar...

[4] https://en.m.wikipedia.org/wiki/CORAL