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Chapter 1. About the NT1 Type 400
LED
READY
ERROR
POWER
If an ERROR indicator is illuminated, check the flash rate of the
READY indicator to determine the source of the error. A faster 8 Hz
flash rate (8 flashes per second) indicates a network problem. A slower
1 Hz rate (1 flash per second) indicates an S/T interface problem.
BASIC RATE DESCRIPTION
ISDN Basic Rate Service consists of two B channels at 64 kbps and a
single D channel at 16 kbps. Basic Rate Service (2B+D Service) pro-
vides a total of 144 kbps to the customer for the transport of voice, cir-
cuit switched data, and packet switched data. Each B channel can be
used for voice or data. The D channel carries the signaling information
needed for call processing. The D channel can also carry packet
switched data using the X.25 protocol.
PASSIVE BUS DESCRIPTION
The S/T interface used to connect to the customer TE has the ability to
connect multiple devices. This arrangement is referred to as the passive
bus and can be used to connect up to eight TEs to the same Basic Rate
line, as described in Appendix B, S/T Bus Configurations on page B-1.
1-2
Table 1-1. NT1 Type 400 Front Panel Indicators
Color
Green
Red
Green
Nt1 T400 User Manual
Description
S/T and U interfaces
ready to place call
S/T or U interface not
ready
Unit has power
61212016L1-20
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