Canon fax basic 2000 Manuale Di Servizio

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BASIC OF TELEPHONE

4. CIRCUIT DIAGRAM IN THE TELE-

PHONE

In this section, let’s learn about the basic circuits inside a telephone.

4.1

Dial Telephones

The Fig. 1-13 shows the basic circuit of a dial telephone.

Fig. 1-13   Basic Circuit of Dial Telephone

However, in actual fact, hook switch HS2 is provided in addition to switch

HS1 on dial telephones as shown in the Fig. 1-14. The bell circuit is closed

and short-circuited by the switch HS2 when the handset is picked up.

Ringing of the bell by dial pulses is thus prevented.

Dial telephones are also provided with a dial shunt contact DS to prevent

noise caused by the entry of dial pulses on the receiver. The DS closes

when you start dialing and opens when the dial has finished returning to its

start position.

Fig. 1-14   Circuit of Dial Telephone

T: Transmitter

R: Receiver

DP: Dial pulse contact

HS: Hook switch

R

T

HS

DP

T: Transmitter

R: Receiver

R

T

DP: Dial pulse contact

HS

1

: Hook switch 1

DP

DS: Dial shunt contact

HS

2

: Hook switch 2

HS

1

HS

2

DS

Bell