بسم الله والحمد لله والصلاة والسلام علي رسول الله وآله وصحبه وإخوانه وسلم
How Analog Phone Works
Inside a Telephone
The very simplest working telephone would look like this
inside.
As you can see, it only contains three
parts and they are all simple:
- A switch to connect and disconnect the phone from the network - This switch is generally called the hook switch. It connects when you lift the handset. On hook means that the circuit is opened.
- A speaker - This is generally a little 50-cent, 8-ohm speaker of some sort.
- A microphone - In the past, telephone microphones have been as simple as carbon granules compressed between two thin metal plates. Sound waves from your voice compress and decompress the granules, changing the resistance of the granules and modulating the current flowing through the microphone.
That's it! You can dial this simple phone by rapidly tapping
the hook switch -- all telephone switches still recognize "pulse
dialing." If you pick the phone up and rapidly tap the switch hook
four times, the phone company's switch will understand that you have dialed a
"4."
The only problem with the phone shown above is that when
you talk, you will hear your voice through the speaker.
Most people find that annoying, so any "real"
phone contains a device called a duplex coil or something functionally
equivalent to block the sound of your own voice from reaching your ear. A
modern telephone also includes a bell so it can ring and a touch-tone
keypad and frequency generator. A "real" phone looks like
this.
Still, it's pretty simple. In a modern phone there is an
electronic microphone, amplifier and circuit to replace the carbon granules and
loading coil. The mechanical bell is often replaced by a speaker and a circuit
to generate a pleasant ringing tone.
ولا تنسوني والمسلمين من صالح الدعاء
وصلي الله وسلم وبارك علي النبي وآله وصحبه وإخوانه وسلم
