t consoles also have a display which provides some in- formation such as the calling name or extension (for internal calls) or the PBX trunk number that the call is coming in on. Even with systems that use direct inward dial numbers and voice mail, there is still typically at least one attendant console which also handles calls returning from unanswered telephones, from voice mail and calls from extensions dialing "0". System Features Accessible To The Desktop Telephone Working With A PBX Outgoing Calls Placing a telephone call to an outside location: On most business telephone systems (PBXs) you dial 9, wait for an outside line dial tone, and dial the telephone number. You then hear a ring- ing signal that is sent to you from the local telephone company central office to let you know that the other end has not yet an- swered. You are not hearing the actual ringing of the telephone you have called. On other systems (smaller Key Systems), when you pick up the handset you already have an outside line dial tone and need only dial the telephone number, without dialing 9. Dialing 9 has become an accepted convention. There is not a technical reason that a telephone system cannot be set up to dial a 42 The Telecom Handbook CHAPTER 2 different digit for dialing out, provided it has not been used for any other function. Intra-office Calls and Intercoms Placing a call to another telephone inside the office: Most business telephone systems enable you to reach any other tele- phone on the system by dialing the three- or four-digit extension number of that telephone. The called telephone may ring differ- ently (probably a different cadence) to indicate an intra-office call. The display of the ringing telephone may indicate the name of the person who is calling. There are many different types of business intra-office com- munications. In addition to simply dialing another extension number, most systems have other capabilities sometimes known as intercoms. Some are separate group intercoms for a specific department, or there ma