Do You Know? Telcos do not (only) use analog line to deliver your data.
by David Sudjiman ~ July 12th, 2005. Filed under: Tech.We all learned that we use modem to modulate and demodulate the digital signal from computer to analog signal so it can be transmitted through Telco (Telephone Company) lines. Well, this is not exactly true.
It used to be that Telco companies had this slow line to transmit data from another end to another end. However, since the technology for data transmission being more mature, Telco now has the infrastructure lines capable to transmit bigger and faster data (and voice) using digital. This connection commonly known as DS0 (64 kbps) or they might amalgamate 24 DS0s into one called DS1 (commonly known as T1). DS3, known as T3, consists 28 DS1s while E1 are formed from 32 DS0s.
So, why we are still using a modem to modulate/demodulate data from/to PC to Telco line? The data still need to be converted because the line from our house to Telco Central Office (CO) still using analog lines.
Here is an ASCII figure to illustrate.
+----+ digital +-------+ analog +----+ digital +----+ analog +-------+ digital +---+
| PC +--- --- -+ Modem +--- --- + CO +--- --- -+ CO +--- --- + Modem +--- --- -+ PC|
+----+ digital +-------+ analog +----+ digital +----+ analog +-------+ digital +---+
Source: Odom, W 2005, CCNA Intro Exam Certification Guide, Cisco Press, Indianapolis. ISBN: 1587200945.
August 10th, 2005 at 11:47 am
and I guess DS0 is known as ISDN
Salam kenal pak David