Figure D-5. Dcp Frame Format - AT&T DEFINITY 2500 series Network Manual

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The DCP protocol physical level requires a 4-wire data link. Therefore, the data link must be composed of
at least two twisted pairs. The physical interface may include additional wire pairs for spares and auxiliary
power functions. Typically, 4-pair inside building wiring and 8-pin modular jacks are used.
The physical interface consists of 22-, 24-, or 26-gauge inside building wiring. The protocol supports
nonrepeatered cable up to a maximum distance of 5000 feet with 24-gauge wire and up to 4000 feet with
26-gauge wire. However, the maximum distance for specific terminals may be further constrained by other
limitations (e.g., depending on the number of associated modules).
Figure D-5 depicts the DCP frame structure. Each frame consists of four fields. The first is a framing field.
It is a 3-bit field which is used to establish frame boundaries. The second is a 1-bit signaling field. It is
used to transmit terminal and call signaling information between the switch and terminals. The third and
fourth are 8-bit information (I) fields. The I-fields are used to transport customer-generated data and PCM-
coded voice between the digital endpoint and the digital switch.
F
FRAMING
FIELD
Table D-5. DCP versus ISDN-BRI protocol parameters comparison
Aggregate Bit Rate
Frame Rate
Bits per Frame
Information Channels
Info Channel Rate
Signaling Rate
Type Signaling
Configuration
1 FRAME
20 BITS
125 MICROSECONDS
S
I1
SIGNALING
FIELD

Figure D-5. DCP Frame Format

PARAMETER
Two (I1,I2)
point-to-point
COMMUNICATIONS PROTOCOLS
INFORMATION
FIELD (1)
DCP ISDN-BRI
160 kbps
8 kHz
20
Two (B1,B2)
64 kbps
8 kbps
Stimulus Functional
point-to-point
or multipoint
I2
INFORMATION
FIELD (2)
192 kbps
8 kHz
24
64 kbps
16 kbps
D-17