ZyXEL Communications ISDN Terminal Adapter Omni.Net Lite Uživatelský manuál stáhnout pdf (Strana 2)

You cannot convert an existing phone number to ISDN, so if you want ISDN you must

obtain a new directory number.

Broadband alternatives for internet access are ADSL and cable modem. However these

are only just now undergoing trials while ISDN is widely available in Bangkok. Also,

ISDN is a mature and tested technology inexpensively offering multiple services. ADSL

and cable modem access offer a different bundle of features and remain to be proven in

the field. They will be covered in future articles. If you need cost-effective, fast inter-

net access and multiple phone lines now, ISDN is for you.

The Structure of ISDN

Traditional telephone service links each customer with the Central Office using a single

pair of wires carrying electrical currents which vary in frequency and amplitude accord-

ing to the speaker’s voice.

This technology goes back more than a century and was adapted with difficulty to

modern computer communications which signal with ones and zeroes ("digital") rather

than continuously varying voltages ("analogue"). (Computers are really stupid; they

can count only to one.) The intermediary is the modem (MOdulator-DEModulator)

which is what modern man hears screeching everywhere nowadays.

ISDN SYSTEM ARCHITECTURE

The BAI "U" interface carries two 64 kbps B ("bearer") channels and one 16 kbps D ("data")

channel for control, signalling, and low-speed data communication. The PRI "U" interface

carries 30 B channels and one D channel.

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ZyXEL Communications ISDN Terminal Adapter Omni.Net Lite Uživatelský manuál Strana 2