Thanks to modern telephony, connecting with anyone in the world is now instantaneous— but it wasn't always this way. This infographic takes you through the telephone's incredible journey, beginning with its invention in 1876, to what you use to make calls today. Enjoyed this infographic? Check out the original Life of a call post by Switch co-founder and VP of Telephony which inspired this timeline: http://bit.ly/1Lb21QK

1. Part 01 / 03
switch.co
http://bit.ly/1JUEh0m
Source
MARCH 1876
Alexander Graham Bell becomes
the first to patent, widely
disseminate,and develop
telephone technology in the U.S.
Alexander Bell spoke the first
words transmitted through
the telephone, “Mr. Watson,
come here. I want to see you.”
Numbers are mapped
to digits, as seen on
today’s dial pads.
The network type for
telephone communication
changes from Bell’s
original point-to-point
“mesh network” (harder
to maintain) to a “central
exchange” (manually
operated).
1950s
The rotary dial phone and the
mechanical switch eliminate
the need for human operators.
5
1970s
Analog to digital
conversion of voice
is invented
Computer Scientist
Vinton Cerf invents
Transmission Control
Protocol/Internet
Protocol (TCP/IP),
allowing computers
to communicate
with each other.
MODERN TELEPHONY
Signaling System (SS7)
Links call information to caller.
Common Channel Signaling (CCS)
Pairs signaling channel and active
voice channel.
Dual Tone Multi Frequency (DTMF)
Pressable phone numbers emit
sine waves.
6
DIGITIZATION
8000 samples of the raw analog
signal are transmitted over the
Publicly Switched Telephone
Network (PTSN) and interpreted
by a computer chip.
As the number of users grows,
it quickly turns into a mesh
network with way too many
wires to build and maintain.
The answer is a central
exchange. Everyone connects
with one line to the exchange.
Operators at the first
exchanges asked,
“Number please,” before
manually transferring
calls from caller to call
recipient.
Life of a Call
A HISTORY