Canon fax basic 2000 サービスマニュアル

BASIC OF TELEPHONE

1–4

1.3

How do you make a call?

When you call someone, you must take various actions.

Let’s consider each individual action needed for making a call.

(1) You pick up the handset. This means you are making a calling request.

 gets ready to connect you to your party.

(2) The exchange emits the dial tone to indicate it is ready for the called

number.

(3) You dial your party’s number. This is the dialing signal.

(4) When the telephone exchange receives your dialing signal, it attempts

to connect with your party. If your party is free, the exchange will

make the connection, and you will hear a ringing tone.

(5) When the other party picks up the handset, the exchange stops sending

the ringing tone, so that you can have a conversation.

(6) You have your conversation.

(7) You hang up.

When the called number is in use, the calling party hears a busy tone. Even

if the called party hangs up while the caller is listening, the calling party

will still hear the busy tone. So the calling party needs to dial again.

1.4

Voice Frequencies Carried by the Telephone

The human ear can hear sounds with frequencies between 10 Hz and

15,000 to 20,000 Hz. The human voice is composed of many different fre-

quencies. To be able to transmit the full range of hearing over the phone

line would require very high-quality amplifiers and other equipment. Far

more than is practical.

The telephone transmits enough voice frequencies to understand what is

being said; usually between 300 to 3,400 Hz.