A telephone call is a link between the called party and the calling party through a telephone network.
Alexander Graham Bell made the first telephone call on March 10, 1876. By sending a call to his assistant, Thomas Watson, Bell proved his ability to “talk with electricity.” The first words transmitted were “Mr. Watson, come here. I want to see you.”
Because it represented the first effective telephone use, this event has been dubbed Bell’s “biggest success.” He refused to have a telephone in his own house, despite it being his biggest achievement, because it was something he developed by accident and regarded it as a distraction from his major research.
A telephone call can convey standard voice transmission, data transfer when the calling and receiving parties use modems, or facsimile transmission when they use fax machines. The call can be made via landline, a cell phone, a satellite phone, or a combination of these methods. A conference call is when there is more than one called party on a phone call. A party line, often known as a rural phone line, is when two or more network users use the same physical connection.
If the caller’s wireline phone is directly linked to the calling party, the calling party’s phone will ring when the caller hangs up. This is referred to as a “hotline” or “ringdown.” A tone is generally delivered to the calling person to signal that they should begin dialing the desired number. If the calling party cannot dial calls directly, they will be connected to an operator who will place the call for them.
A commercial telephone company’s public network (such as the Public Switched Telephone Network) or a private network is known as a PBX can be used to make calls. A private network is usually linked to the public network to allow PBX users to dial the outside world.
Incoming calls to a private network come to the PBX in one of two ways: directly to a user’s phone via a DDI number or indirectly through a receptionist who will take the call first and then manually connect the caller to the appropriate user on the PBX.
The end-to-end connection for most PSTN calls is established via ISUP signaling messages or one of its variations between telephone exchanges. QSIG, DPNSS, or variations are used to set up calls over PBX networks.
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