Common Ethernet Systems
10BASE-5 or (Thick Ethernet)
10BASE-5 is the original Ethernet system. It employs a quarter of an inch diameter, 50 ohm coax cable ( with minimum bend radius of 10 inches). 10BASE-5 segments can run in length up to 500 meters with as many as 100 transceiver connections spaced at lease 2.75 yards apart.
10BASE-5 transceivers access the media by piercing the thick coaxial cable. These transceiver taps are known as vampire taps. Since they don't actually require breaking the physical cable, the electrical signals over the cable are typically fairly clean.
10BASE-5 systems were originally envisioned to be cheap and fairly easey to build. The large cable needed simply to be run by rooms where computing equipment would be located. Taps would be made into the cable by using external transceivers. As it turned out, the requirement of an external transceiver and the thick cable, which was expensive and difficult to work with, limited the use of 10BASE-5.
10BASE-2 (Thin Ethernet)
Thin Ethernet was a fairly popular specification and is still used in many environments today. With a maximum segment length of 203.5 yards, it requires that the 50 ohm cable be only .2 inches thick ( a bend radius of two inches). It also uses standard BNC connectors and "T's" to provide access to the media. Typically, T's are connected directly to the back of network interface cards, thus eliminating the need for an external transceiver.
A maximum of 30 transceivers may be inserted onto a Thin Ethernet segment and must be spaced at least 20 inches apart. 3Com hardware is able to handle slightly longer segments, up to 220 yards in length. Unfortunately, mixing other vedor's equipment into an environment where cable runs exceed 203.5 yards can cause problems. For this reason, keeping total lengths to 203.5 yards is recommended.