ends upon how the system is programmed. Conference Calls Most telephone systems are equipped with a conference but- ton on the telephone. This enables you to set up a conference among three or more people, connecting people within your of- fice to others outside the office. Systems vary in the number of inside and outside callers that can be conferenced. Typically, it becomes hard to hear on a conference call with more than three participants unless you are using specialized conferencing equip- ment that is separate from the telephone system. For conferences of more than three or four people, it is advis- able to use special conferencing equipment (called a conference bridge) or an outside conferencing service. It is important to know how to drop off one of the conferees from your conference call without ending the call. Not all systems can do this. If you have The Telecom Handbook % 45 THE PBX set up the conference call from your telephone and you hang up, you may disconnect the other call participants. Last Number Redial Many telephones store the telephone number you have just dialed SO that if you reach a busy signal and wish to try again you need only press the last number redial button. On some telephones you do not need to lift the receiver to do this. Press- ing the redial button will activate the speakerphone. Some telephones have a similar feature called save and repeat. This usually takes up two buttons and enables you to place other calls while the telephone still retains the number you want to retry at a later time. Speed Dialing and Automatic Dialing These capabilities enable you to store frequently called tele- phone numbers in your telephone. Then you need only press one or a few buttons rather than dialing the entire telephone number. If you have spare flexible feature buttons on your telephone, these can often be set up to automatically dial a telephone number by pressing just that one button (typically called Automatic Dialing or Autodial). Or there may be a button for speed dial that you press,