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Transmission rate
• Downstream
• up to 6–8 Mbit/s
• up to 1.5 Mbit/s for G.lite
• Upstream
• up to 640 Kbit/s
• up to 512 Kbit/s for G.lite
Line code
• DMT
• CAP
Number of pairs
• one pair
Usage
• public network operators (PNO) and Internet service providers
Restrictions
• Asymmetry
4.1.2 ISDN DSL technology
The IDSL technology is based on the ISDN technology, but without switching. IDSL uses 2B1Q
line encoding and has two B and one D channel capacity, which allows transmitting data bi-
directional at 144 Kbit/s. The necessity to transmit simultaneously voice and data served as a
powerful spur to the further development of IDSL. Thus, the channel capacity is divided between
voice unit and digital interface. NTU-128 Voice is an example of a device implementing this
mode,
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