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| Transmission Rates | |
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ISDN utilizes groups of standard transmission channels. Bearer channels (or B channels) transmit user information at relatively high speeds, while separate Delta channels (or D channels) carry call setup, signaling, and other information. ISDN Basic Rate Interface Service (BRI) connects the ISDN office to the user location and provides access to three channels.
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The channels can be provisioned as follows: |
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B1 - Voice, Data, B channel Packet (high speed 64Kb) |
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| B2 - Voice, Data, B Channel Packet (high speed 64Kb) | |
| D - Signaling, D Channel Packet (low speed 16Kb) | |
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ISDN
Primary Rate Interface service (PRI) provides digital access
via a T1 line with a 1.544 bandwidth. This bandwidth is divided
into 24 64Kb channels.
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The
ISDN PRI service uses 23 of the T1 channels to provide B
channel access and uses the 24th channel for signaling purposes.
ISDN call control procedures use packetized messages to initiate,
monitor, and release connections. In a BRI call, these messages,
along with other call control messages are routed via the D channel
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