Employees at Bellcore ( now Telcordia Technologies ) developed Asymmetric Digital Subscriber Line ( ADSL ) by placing wide-band digital signals above the existing baseband analog voice signal carried between telephone company telephone exchanges and customers on conventional twisted pair cabling facilities, and filed a patent in 1988.
42.
The first HIPPI standard defined a 50-wire twisted pair cable, running at 800 Mbit / s ( 100 MB / s ) with maximum range limited to 25 meters, but was soon upgraded to include a 1600 Mbit / s ( 200 MB / s ) mode running on Serial HIPPI fibre optic cable with a maximum range of 10 kilometers.
43.
Twisted pair cabling must be used with RJ48, T568A and T568B . Twisted-pair data patch cable used with the three data standards above is not a direct replacement for RJ61 cable, because RJ61 pairs 3 and 4 would be split among different patch cable twisted pairs, causing cross-talk between voice lines 3 and 4 that might be noticeable for long patch cables.
