Practical TCP/IP and Ethernet Networking- P14: The transmitter encodes the information into a suitable form to be transmitted over the communications channel. The communications channel moves this signal as electromagnetic energy from the source to one or more destination receivers. The channel may convert this energy from one form to another, such as electrical to optical signals, whilst maintaining the integrity of the information so the recipient can understand the message sent by the transmitter | Ethernet networks 47 frame transmission by the MAU the SQE signal is asserted to ensure that the circuitry remains active and that collisions can be detected. You should be aware that not all components support SQE test and mixing those that do with those that don t could cause problems. Specifically if a NIC was to receive a SQE signal after a frame had been sent and it was not expecting it the NIC could think it was seeing a collision. In turn as you will see later in the manual the NIC will then transmit a jam signal. 10Base2 systems The other type of coaxial cable Ethernet networks is 10Base2 and often referred to as Thinnet or sometimes thinwire Ethernet . It uses type RG-58 A U or C U with a 50-ohm characteristic impedance and of 5 mm diameter. The cable is normally connected to the NICs in the nodes by means of a BNC T-piece connector and represents a daisy chain approach to cabling. Connectivity requirements include It must be terminated at each end with a 50-ohm terminator The maximum length of a cable segment is 185 meters and NOT 200 meters No more than 30 transceivers can be connected to any one segment There must be a minimum spacing of meters between nodes. It may not be used as a link segment between two Thicknet segments The minimum bend radius is 5 cm The physical layout of a 10Base2 Ethernet segment is shown in Figure . Figure 10Base2 Ethernet segment The use of Thinnet cable was and remains very popular as a cheap and relatively easy way to set up a network. However there are disadvantages with this approach. A cable fault can bring the whole system down very quickly. To avoid such a problem the cable is often taken to wall connectors with a make-break connector incorporated. The connection to the node can then be made by fly leads of the same cable type. It is 48 Practical TCP IP and Ethernet Networking important to take the length of these fly leads into consideration in any calculation on cable length There is also provision .
