Auto-transformers in LAN magnetics

Hi People,

Would love to know the purpose of using Auto-transformers in LAN magnetics. I came across this term while searching for magnetics.
Whats the difference between magnetics with and without using Auto-transformers?

Filters common mode noise to provide signal integrity and protects chip, provides DC isolation, offers low mode conversion. The term "magnetics'' refers to the one-to-one isolation transformers and common mode choke transformers which couple the signal to and from the twisted pair media.
In most electrical signal transmission systems, the data moving between two nodes is AC coupled in order to isolate potential system ground differences between the transmitter and receiver which could interfere with proper signal transfer. A one-to-one isolation transformer is a convenient component for use in signal transfer for several reasons: DC
current blocking (system ground differences are isolated from one another), end stations protection from static charges that may build up on the cable, inherent differential signal coupling and common mode rejection.

**broken link removed**
http://www.datasheetcatalog.org/datasheets2/21/214632_1.pdf

Generally L/C Magnetics provide Auto Transformers as an open core and coil unit, which enclosed in an indoor enclosure with corrosion resistant power coating.