ompany to reduce your mainte- nance cost, since it is often based upon the number of ports used for outside lines. You must also have your telephone system re- programmed SO that it will not be looking for the missing lines when someone dials 9 or, in the case of your DID trunks, when a call comes in. Here's another situation for which you may wish to run a traffic study. Callers to your organization complain that they are reaching a busy signal. The one-week traffic study shows that all 20 outside lines are in use ten percent of the time, confirming that during this time callers cannot reach your company. You or- der 5 more local outside lines from the local telephone company and have them connected to your system by the telephone instal- lation company. You may need to buy an additional circuit board 52 The Telecom Handbook CHAPTER 2 for the system to accommodate these new lines. Several weeks later you run another traffic study that shows that at the busiest times of day, no more than 22 lines are in use. Callers cease to complain about busy signals. The traffic study also measures call volume on T-1 circuits. It's a good idea to have a traffic study run on your telephone system at least once a year. You may negotiate an annual traffic study as a part of your PBX maintenance contract. Or you may learn how to run the traffic study in-house with your call ac- counting system. MAC (Moves and Changes) Many companies spend thousands of dollars moving tele- phones around the office and changing the extensions or features on the telephone. This activity is MAC work (MAC = moves and changes). It can be provided by your telephone installation com- pany. Most PBXs enable you to do some of your own MAC work using a PC with software that makes program changes to the PBX. In some older systems, the changes may be done with a keyboard only or a dumb terminal. For example, two executives are exchanging offices. It is nec- essary to change the extensions appearing on the telephones in each of the offices, on the secretaries' 