Stations must listen for a carrier on the wire. If no carrier is detected, stations can begin transmitting. While transmitting, the station continues to listen on the wire to ensure successful communications. If two stations attempt to transmit information at the same time, the transmissions overlap and cause a collision.

If a collision occurs, the transmitting station recognizes the interference on the network and transmits a bit sequence called jam. The jam helps to ensure that the other transmitting station recognizes that a collision has occurred. After a random delay, the stations attempt to retransmit the information and the process begins again.

The Ethernet cable and a standard telephone cable do look alike but are very different. The Ethernet cable is know as a "category 5 cable" or "cat 5" for short. The ends of a cat 5 cable are also wider than a telephone cable because this type of cables have more pins in the ends. Because of these design difference a telephone cable and a Ethernet cable are not interchangeable.

Yes, there are many, and they vary according to the media used. First of all, there are distance limitations: 10Base-2 limited to 185 meters (607 ft) per unrepeated cable segment. 10Base-5 limited to 500 meters (1,640 ft) per unrepeated cable segment. 10Base-F depends on the signaling technology and medium used but can go up to 2KM. 10Base-T generally accepted to have a maximum run of 100-150M, but is really based on signal loss in db's (11.5db maximum loss source to destination).

Then there are limitations on the number of repeaters and cable segments allowed on a single network. There may be no more than five (5) repeated segments, nor more than four (4) repeaters on any Ethernet; and of the five cable segments, only three (3) may be populated. This is referred to as the "5-4-3" rule (5 segments, 4 repeaters, 3 populated segments). It can really get messy when you start cascading through 10Base-T hubs, which are repeaters unto themselves. Just try to remember, that any possible path between two network devices on an unbridged/unrouted network cannot pass through more than 4 repeaters or hubs, nor more than 3 populated cable segments.

Finally, 10Base-2 is limited to a maximum of 30 network devices per unrepeated network segment with a minimum distance of 0.5m (1.5ft) between T-connectors. 10Base-5 is limited to a maximum of 100 network devices per unrepeated segment, with a minimum distance of 2.5m (8.2ft) between taps/T's (usually indicated by a marker stamped on the cable itself every 2.5m).

The fact that the word "modem" is used to describe this device can be a little misleading only in that it conjures up images of a typical telephone dial-up modem. Yes, it is a modem in the true sense of the word; it modulates and DEModulates signals. But the similarity ends there because cable modems are practically an order of magnitude more complicated than their telephone counterparts.

Cable modems can be part modem, part tuner, part encryption/decryption device, part bridge, part router, part network interface card, part SNMP agent, and part Ethernet hub. Typically, a cable modem sends and receives data in two slightly different fashions.

In the downstream direction, the digital data is modulated and then placed on a typical 6 MHz television channel, somewhere between 50 MHz and 750 MHz. Currently, 64 QAM is the preferred downstream modulation technique, offering up to 27 Mbps per 6 MHz channel. This signal can be placed in a 6 MHz channel adjacent to TV signals on either side without disturbing the cable television video signals.

The upstream channel is more tricky. Typically, in a two-way activated cable network, the upstream (also known as the reverse path) is transmitted between 5 and 42 MHz. This tends to be a noisy environment, with RF interference and impulse noise. Additionally, interference is easily introduced in the home, due to loose connectors or poor cabling.

Since cable networks are tree and branch networks, all this noise gets added together as the signals travel upstream, combining and increasing. Due to this problem, most manufacturers use QPSK or a similar modulation scheme in the upstream direction, because QPSK is more robust scheme than higher order modulation techniques in a noisy environment. The drawback is that QPSK is "slower" than QAM.