N-ISDN (Narrowband Integrated Switch digital Network) was an attempt to replace the analog telephone system with a digital one.
It generally uses 64 kbit/s channel as the basic unit of switching. It has a circuit switching orientation.
N-ISDN basic rate is too low so for home as for business today. N-ISDN may be partly saved, but by an unexpected application: Internet access. Various companies now sell ISDN adapters that combine the 2B + D channels into a single 144 kbit/s digital channel. Many Internet providers also support these adapters. So the people can access the Internet over a 144 kbit/s digital link
Narrowband refers to data communication and telecommunications tools, technologies and services that utilize a narrower set or band of frequencies in the communication channel. These utilize the channel frequency that is considered flat or which will use a lesser number of frequency sets.
Narrowband is typically implemented in telecommunication technologies to carry voice data on a limited number of frequency sets. The size of the message sent via a narrowband technique utilizes lesser bandwidth than the cumulative bandwidth of the underlying channel.
Narrowband is also used in sending audio spectrums that consume a restricted range of frequencies. The US FCC has allocated a specific range of frequency for mobile radio services based on narrowband that spans from 50cps to 64kbit/s.
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