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| n |
PSTN switching
is based on circuit switching by duplex*
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connections
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| n |
Temporary bidirectional
connections
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| n |
Originally for speech
(voice) only at 300-3400 Hz
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| n |
Earlier two
subscribers connected by purely physical
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connection
(physical switch contacts)
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| n |
Nowadays by time
slots ~ ISDN is integrated to PSDN
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| n |
PCM is
the TDMA standard for the digital transmission
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| n |
PCM time slots
consist of 8 bit samples
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| n |
For voice
digital exchange sets up 64 kbit/s connections
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| n |
Data
connections by (1) modems, (2) ISDN interface
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(3) leased lines
via X.25 / Frame relay, or (4) ADSL
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