 may be used to plug the computer into a separate outside line, bypassing the PBX or an extension from the PBX, which can be used by the computer as a dial back up for Internet access, should the LAN connection to the Internet be out of service. The fourth 250 The Telecom Handbook CHAPTER 12 Figure 12.2 Faceplate With 4 Jacks VOICE may be used for a fax machine or some other telecommunica- tions device. There is a lot to be said for running more cable to each desk than you think you will need. Some applications use all four pairs in the cable for one high speed transmission path. It is also important to make the cable accessible. Having to remove the jack and reach behind the wall to pull out another pair of cables can create a messy appearance, be cumbersome perform, and may disrupt other devices already working at that location. Power at the Desk Another related consideration is having a sufficient number of electrical outlets at each desk to accommodate everything that requires power. Most traditional telephones do not require sepa- rate power. The required amount of power can be sent from the telephone equipment room over a separate pair of wires (low voltage) going into the same jack as the telephone. Certain tele- phones may require an electrical outlet at the desk, SO it is always a good idea to ask if it is necessary. For example, modules used to expand the number of extensions appearing on the telephone may require power at the desk. Some speakerphones enabling The Telecom Handbook % 251 CABLE hands-free conversation also require separate electrical outlets. Also some early IP (Internet Protocol) Telephones require power at the desk, although the newer ones do not. Main and Intermediate Distribution Frames We have talked about UTP copper cable and how it is termi- nated at the desk. What happens at the other end of that cable? If all cables in the installation are home run that means that they all pull back to the same place, which is the MDF (Main Distribution Frame). It is a good idea to place the MDF 