Telephone Systems for Every Need
There are two primary types of telephone systems in use. These are private telephones that are located in your home and commercial systems like those found in office buildings. There are three methods that have been used by phone companies that have been used to connect your calls. Public Switched Telephone Networks (PSTN) Public switched telephone networks are what your home phone is connected to. In a public switched network, your home phone is connected, along with all other home phones, as well as business phone networks, to a central office where the switching and routing that connects you to the phone you're calling occurs. Private Branch Exchanges (PBX) Private branch exchanges are used by companies that normally have multiple phone lines that usually serve a single number. The original type of PBX had an operator that would physically connect an incoming call to the desired extension. As technology evolved, this switching was able to be done electronically. In most examples of a PBX, the caller is asked to dial the desired extension. Other types will have the company operator make this connection. To get an outside line, an internal user must dial a single number (usually nine or six), wait for the dial tone, then dial the outside number. An identifying feature of most PBX systems is the relatively large telephone system controller in a main telecommunications room. Key Systems The main differentiating feature between a PBX and a key system-based commercial phone network is that in a key system network, the internal user must select the outside line to call on, normally by pushing a button on the phone that corresponds to that line. You can recognize this type of system with older phones that have the translucent buttons below the number pad that light up to indicate a line that is in use. Methods of Connecting Calls in Telephone Systems When the first telephones were introduced, they were bulky and had a hand crank on the Telephone Company Dubai side. The user would pick up the speaker from the cradle and crank the handle. This would send an electrical signal to the central office where that phone's line would ring, and an operator would plug her headset into a corresponding receptacle, the caller would tell the operator who they were calling. The operator would then make the physical connection by plugging a cord from one phone line into the other phone line. The dial telephone was the first major innovation in telephone systems. The operator had been made almost unnecessary with this system. The caller would lift the receiver and turn a rotary dial to a stop and release it, creating a series of clicks, or pulses that corresponded to the number being dialed. The next major innovation was the tone dialing system, in which each number is assigned a unique tone. The computer in the central office translates these tones into the number being dialed and routes the call accordingly. |