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Old 23rd Feb 2021, 8:44 pm   #6
G6Tanuki
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Join Date: Apr 2012
Location: Wiltshire, UK.
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Default Re: Finding old ISDN PRI terminals?

Yes what Canford was pushing was "Basic Rate" ISDN: two separate 64Kbit/sec channels (56Kbit/sec in the US) and a background 16Kbit/sec 'data' channel. Perfect for providing "CD Quality" digital audio between a home-studio and the actual transmitter-infrastructure. The likes of ClassicFM could not have launched without it!.

"PRI" - Primary Rate Interface - ISDN was much heavier-duty: you got a 2.048Mbit/sec pipe [1.536Mbit/sec in the US] channel that could be subdivided to provide loads of separate voice-quality audio channels [for speech-phones] or multiple sub-channels could be 'aggregated' to provide something like 320Kbits/second which was just-about-adequate for videoconferencing.

As noted upthread, this was generally done using 'professional'-grade hardware: I remember some of the Cisco Call-Manager gear from the last-century came with options for PRI cards, and Codian also offered a range of hardware-codecs that could rate-translate between popular US and UK videoconferencing bit-rates.
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