Re: [telecom] T4 and T5 carrier systems

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- Fred Goldstein
  
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posted
5 years ago

Mon, Mar 11, 2019 2:10 PM

Does anyone know of original sources or other credible references for
> the specifications or design and implementation of the T4 or T5 > carrier systems? >

I don't think there was ever such a thing as T5, on paper or elsewhere.

The DS4 rate was 274.176 Mbps, meant to be on coax, using "polar" coding (according to a 1980s-vintage textbook). But I doubt it was ever put into volume production.

- - Fred R. Goldstein k1io fred "at" ionary.com

***** Moderator's Note *****

Lost-in-the-mists-of-time department: IIRC, T5 was never implemented, because fiber was being rolled out and there weren't enough coax cables. But, I may be wrong: does anyone recall when fiber became commonly available?

Bill Horne Moderator

- D
- David
  
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posted
5 years ago

Tue, Mar 12, 2019 5:30 AM

There were "digits over coax" unit from Philips applied to L4/L5 coax; they were trouble-plagued. One issue was the higher imposed voltage led to arcing.

I have a plat showing FT7 being installed in 1981. This route starts in the Washington 2 CO and runs along Rt. 29 north of Silver Spring MD, headed for York PA.

This is an *old* route with many upgrades. Near as we can tell:

1941: original easements, K-Carrier, maybe L1 as well.

1946/7 Upgraded to L2

1959: L3, many 4-mile spaced huts added

1981: FT7 multi-mode with 4-mile spaced regenerators colo'ed at L3huts

????: Single-mode deployed; L3+FT7 huts abandoned.

- M
- Michael Moroney
  
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posted
5 years ago

Thu, Mar 14, 2019 9:18 PM

When things went to fiber, what kind of signalling was used? Was it digital from the start and similar to the DS1/DS3 signalling? Is what used now all packets like on a computer LAN?

Also what about Verizon FIOS to a home, do they piggtback the phone/TV on the IP link, or perhaps the other way around the piggyback the IP on a TV band like cable companies do?

I have no idea about "commonly available", but I do remember ads from the

70s where they show this big fat zillion conductor copper phone cable being yanked into a conduit, followed by this tiny thin cable with light coming out of its end, coming back out of the conduit, and ATT boasting that it could carry many times more phone calls than the copper cable. Must be early-mid 70s.