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Chapter 8. FireWire > 1394b Twisted Cable Physical Layer Attributes

8.4. 1394b Twisted Cable Physical Layer Attributes

8.4.1. Shielded Twisted Cable

To distinguish 1394b ports from those of traditional FireWire, a new connector with reversed contact orientations as shown in Figure 8.27 has been defined. The plug, as shown on the left side of the figure, has contacts on top and beneath bottom sides of an almost rectangular post in contrast with those inside a cavity. Correspondingly, contacts are inside the cavity of the new 1394b socket as indicated on the right side of the figure. Nine contacts are defined with two additional pins, 5 and 9, for connecting shields of these two twisted pairs and one additional pin, pin 7, which has been reserved for future use. Pins 6 and 8 are used for power supply, pins 1 and 2 belong to one shielded twisted pair, and pins 3 and 4 belong to the other pair. Some FireWire ports can operate in either traditional or 1394b modes. A cable with a traditional plug at one end and a new plug at the other end can be used to connect a traditional FireWire port and a bilingual port. A key, as shown at the bottom side of the plug and the socket, is designed to separate a 1394b-only port from a bilingual port. The key on a bilingual port, both plug and socket, is a little narrower than that of a 1394b-only port. Therefore, a 1394b-only plug can be inserted in both 1394b-only and bilingual ports while a bilingual plug will not fit a 1394b-only socket.

Figure 8.27. Beta and Bilingual Connectors (From IEEE Std. 1394B-2002. Copyright © 2001 IEEE. All rights reserved.)



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