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2.5
Dial
Dialling enables an exchange to connect one party to a requested number
according to a dialing signal. "DP" means the Dial pulse contact. The con-
tact is usually closed. When you turn a dial and release it, the contact
opens the same number of times as the number you dialed. (When the
dialed number is 0, the contact opens 10 times.)
When a DC loop is made as shown in the Fig. 1-11 and the dial returns to
its start position after the number "4" is dialed, the DC loop is cut four
times. This is called the "dial pulse".
Dialing using this dial pulse is called "pulse dial" due to the fact that num-
bers are dialed by this pulse.
The exchange selects and calls up the other party by counting the number
of dial pulses.
Dials return to their start position at either of two speeds:
PPS (Pulse Per Second) indicates how many dial pulses are generated per
second.
OFF
DP
ON
HS (Off-hook state)
7
ON
DP
OFF
Dial return
• 10PPS
• 20PPS
T: Transmitter
R
R: Receiver
DP: Dial pulse contact
HS: Hook switch
T
4
3
5
2
6
1
8
9 0
Fig. 1-11 Dial Pulse
BASIC OF TELEPHONE
1–9
1
2
3
4
5
6
ït
çi
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