0BASE-FX permits the maximum network diameter of 200 m for 100BASE-TX to be extended to 400 m. However, in a mixed 100BASE-T4- 100BASE-FX environment the maximum collision domain should not exceed 231 m, consisting of 100 m for 100BASE-T4 and 131 m for 100BASE-FX. Both ST and SC fiber connectors that were originally defined for FDDI are supported by 100BASE-FX. TABLE 5.2 Multimode Fiber 10BASE-FL versus 50/125 50/125 50/125 62.5/125 83/125 100/140 FOIRL Optical Numerical aperture 0.275 Attenuation 10BASE-FL loss budget, dB FOIRL loss budget, dB Chapter Five REPEATER RULES Two types of repeaters are specified for use in a Fast Ethernet environment: class I and class II. CLASS I REPEATER A class I repeater has a greater budget for timing delay, enabling the device to support dissimilar physical media segments that use different signaling methods. The delay for a class I repeater is 140 bit times. In one example of the use of a class I repeater, a 100BASE-T4 seg- ment that uses 8B6T coding is connected to a 100BASE-X segment that uses 4B5B coding. Here the greater timing delay enables a class I repeater to translate the line signal received on one port to the line signal required on the distant segment. Only one class I repeater can be installed in the same segment. CLASS II REPEATER The second type of Fast Ethernet repeater is a class II device. The class II repeater has a lower budget for timing delay; hence it is faster than a class I register. The delay of a class II repeater is 92 bit times. Up to two class I repeaters can be used in a segment, with up to one 5-m interrepeater cable length permitted. Because a class II repeater immediately repeats an incoming signal, it can be used only to intercon- nect segments that use the same signaling method, such as 100BASE-TX and 100BASE-FX. SPAN DISTANCE According to the preceding observations, the actual span distance obtainable through the use of repeaters in a Fast Ethernet environment depends on the type of repeaters used and the media employed. Figure 5.11 summari