Traditional Telephony

The Traditional Telephony section discusses the legacy public switched telephone network. As the world migrates from the traditional world of telphony to VoIP, you need to know both worlds. Here's a look at the legacy devices and protocols used that keep the global phone system working.

Legacy Interfaces - This area discusses the legacy interfaces used by the PSTN: FXO. FXS, T1, E1, ISDN BRI and PRI.

Telephone Line Characteristics - This area discusses running the characteristics of the analog telephone line: voice channel, telephone line characteristics, attenuation distortion, propagation delay, envelope delay distortion, line impairments, crosstalk, echo or signal return, frequency shift, non-linear distortion, jitter and transients.

Modems - This section discusses the digital modulation schemes used for transmission, dial-up modems, ADSL modems and Cable modems.

Multiplexing -This area discusses the principles of multiplexing, frequency division multiplexing, time division multiplexing and statistical time division multiplexing.

X.25 - This section details a very old protocol that has provided the foundation for many other protocols that followed. While it is rarely used, it does have some unique characteristics that are worth mentioning.

Frame Relay - This section details the Frame Relay protocoal that is commonly used throughout the legacy telephony network. It is X.25 on steriods and many Frame Relay concepts were used during the development of MPLS

Signaling System No. 7 (SS7) - This section details the SS7 protocol that is used to setup and tear down calls throughout the public switched telephone network (PSTN).

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Copyright July 2013 Eugene Blanchard