ne workstation is forwarded to the reception pair of all other workstations, but not to its own reception pair. For collision detection the workstation merely needs to detect a signal on the reception pair. If a signal is received before its own transmission is termi- nated, someone else has transmitted at the same time and a collision has occurred. When a workstation is connected to a hub it operates in half- duplex mode, that is, it can either transmit or receive at a time. The 10BaseT uses Manchester coding similar to that used by a coaxial network but symmetrically SO that the signal voltage varies between + 1V and -1V instead of OV and -2V. Bit values are encoded into transitions + or + as shown in Figure 6.28 and care must be taken not to invert two conductors of a pair. The requirements for a 10BaseT network collision detection feature to operate properly are exactly the same as those for a coaxial network. We have to take care that the worst-case propagation delay from one station to the most distant station does not exceed half of the transmission time of the shortest frame. At 10 Mbps this requirement is the same as in the coaxial net- works, that is, there may be five cable segments and four repeaters (hubs) on the transmission path between two workstations. The twisted pair restricts the transmission distance between a concen- trator and a workstation to approximately 100m. Note that when the data rate is increased, the duration of the shortest frame is decreased and the maxi- mum distance is correspondingly decreased. A 10BaseT network can be extended by connecting hubs together with a twisted pair or fiber segment. In this structure one workstation in Figure 6.31 is simply replaced by another hub as shown in Figure 6.32. In the network that we just described, all frames are transmitted to every segment in the LAN. We call this shared media CDMA/CD because all computers share the transmission capacity. The shared media networks shown in Figures 6.26 and 6.31 make up a single "collision domain"; that 