Central office switches are used to route circuit-switched digital network calls. There are two types: end office switches route local calls and offer services like call forwarding, while tandem switches route long distance calls across the public switched telephone network. The document also discusses analog vs. digital signals, integrated services digital network (ISDN) which allows phone and internet use simultaneously, and fiber-optic cables which carry data over long distances faster than electrical cables.

1. How Circuit-Switched Digital
Networks Work
● Analog and digital signal
● What is Central office switch?
● Fiber-optic
● IDSN
s1170132 Manamu Abe
s1170133 Keigo Amma
s1170144 Ryo Kanno
s1170145 Masataka Kubota

2. What is Central office switch?
Central office switch
is the generic name
for two switches, end
office switch and
tandem switch.
End office switch is
used for services
such as call
forwarding and call
waiting.
Tandem switch is
used for long distance
communication in the
PSTN.

3. Analog and digital signal
● The analog signal is a
signal expressed with
physical quantity such
as the voltage or the
electric current, and
the digital code is a
signal expressed with
numerical value.

4. ISDN
● ISDN (Integrated Services
Digital Network) is digital
transmission for the telephone,
FAX and other data.
● ISDN consists of 3 channel.
2 channel of them are for the
transmission, and the other
one is for the control.
● Therefore, we can use the
telephone and Internet at the
same time.

5. Fiber-optic
● Fiber-optic is often called
optical fiber.
● An optical fiber is a glass
or plastic fiber that carries
light as data.
● It can carry data for short
time than electrical
cables.So optical cable is
used in many locations

6. REFERENCE
 Your Dictionary.com
http://www.yourdictionary.com/
 Network dictionary
http://www.networkdictionary.com/
 Analog and digital signal
http://www.networkworld.com/subnets/cisco/081308-ch
 Wikipedia
http://en.wikipedia.org/wiki/Optical_fiber