er you will be able to make it work to complement your operations. Each telephone system installation company has people on staff who understand the PBX their company sells. If a company sells or supports too many different PBXs, the likelihood of staff knowing any one of them well diminishes. Most telephone installation companies' knowledge is based upon the collective experience of their staff. No one person knows everything there is to know about a particular PBX. There is just too much to know and it changes with different software re- leases and system configurations. What the telephone installa- tion company does not know, you may be able to find out from the PBX manufacturer. If you are responsible for managing a telephone system, you may wish to join a user group. These groups exist for all of the major PBXs. People using systems in real world environments are often the best source of information on a particular system. What is the Physical Makeup of the PBX? The PBX is made up of hardware and software components that serve the purpose of connecting the telephones to outside lines enabling the completion of incoming and outgoing calls. The PBX also connects internal calls from one telephone in the office to another. The PBX is typically housed in the telecommunications equip- ment room or closet on the premises of an organization. It is comprised of one or more metal cabinets housing the electronic components. PBXs from different manufacturers may look dif- ferent. Some cabinets are the size and shape of a refrigerator and 22 is The Telecom Handbook CHAPTER 2 may line up side-by-side in the larger systems. Some are modu- lar, with each module stacking on top of another, three or four high. A smaller PBX cabinet may mount on the wall. Some cabi- nets have metal doors SO you cannot see inside and others have black plexiglass doors showing off the blinking colored lights and complex looking circuit boards inside. Here is an example of what a PBX may look like: Figure 2.1 Appearance of Typical PBX Cabinet 4 S