While in your world many of the older technologies of data communications may be replaced with modern one, there are many reasons why you may need to know about them. You may get a better understanding of how things are done on your current network if you understand the evolution of the network.
If you ever work in consulting you may be surprised to find out how much of what you call obsolete is still in use. You will also find questions on older technologies on various certification tests.
Data communications definitions:
In the early days of connecting your computer to the internet most folks had Public Switched Telephone Network (PSTN), also referred to as Plain Old Telephone Service (POTS), and all connections were run over the standard copper phone lines. In order for the digital world of computers to talk over analog phone lines you needed to use a MODEM.
The term MODEM comes from the words modulator and demodulator, it is a device that modulates a carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data.
Modem standards, or V dot modem standards, are defined by the ITU (International Telecommunications Union). The FCC has limited the speed of analog transmissions to 53 Kbps
Twisted pair cabling is a common form of wiring in which two conductors are wound around each other for the purposes of canceling out electromagnetic interference which can cause crosstalk. The number of twists per meter make up part of the specification for a given type of cable.
The two major types of twisted-pair cabling are unshielded twisted-pair (UTP) and shielded twisted-pair (STP).
UTP - Unshielded Twisted Pair; uses RJ-45, RJ-11, RS-232, and RS-449 connectors, max length is 100 meters, speed is up to 100Mps. Cheap, easy to install, length becomes a problem. Can be CAT 2,3,4 or 5 quality grades.
In shielded twisted-pair (STP) the inner wires are encased in a sheath of foil or braided wire mesh. Shielded Twisted Pair uses RJ-45, RJ-11, RS-232, and RS-449 connectors, max length is 100 meters, speed is up to 500Mps. Not as inexpensive as UTP, easy to install, length becomes a problem. Can be CAT 2,3,4 or 5 quality grades.
Category 1 Traditional UTP telephone cable can transmit voice signals but not data. Most telephone cable installed prior to 1983 is Category 1.
Category 2 UTP cable is made up of four twisted-pair wires, certified for transmitting data up to 4 Mbps (megabits per second).
Category 3 UTP cable is made up of four twisted-pair wires, each twisted three times per foot. Category 3 is certified to transmit data up to 10 Mbps.
Category 4 UTP cable is made up of four twisted-pair wires, certified to transmit data up to 16 Mbps.
Category 5 UTP cable is made up of four twisted-pair wires, certified to transmit data up to 100 Mbps.
Twisted-pair Ethernet cable has the following specifications:
100BASE-TX specification uses two pairs of Category 5 UTP or Category 1 STP cabling at a 100 Mbps data transmission speed. Each segment can be up to 100 meters long.
100BASE-T4 specification uses four pairs of Category 3, 4, or 5 UTP cabling at a 100 Mbps data transmission speed with standard RJ-45 connectors. Each segment can be up to 100 meters long.
Fiber optic cable (IEEE 802.8) in which the center core, a glass cladding composed of varying layers of reflective glass, refracts light back into the core. Max length is 25 kilometers, speed is up to 2Gbps but very expensive. Best used for a backbone due to cost.
100BASE-FX specification uses two-strand 62.5/125 micron multi- or single-mode fiber media. Half-duplex, multi-mode fiber media has a maximum segment length of 412 meters. Full-duplex, single-mode fiber media has a maximum segment length of 10,000 meters.