AT&T 7100 series, 7500 series, 2500 series, 7200 series, 7400 series, 7300 series manual Or multipoint

COMMUNICATIONS PROTOCOLS D-17

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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-5depicts 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.

1 FRAME

20 BITS

125 MICROSECONDS

F

S

I1

I2

FRAMING		SIGNALING		INFORMATION		INFORMATION
FIELD		FIELD		FIELD (1)		FIELD (2)
		Figure D-5.DCP Frame Format
	Table D-5.DCP versus ISDN-BRI protocol parameters comparison
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	⎜	PARAMETER	⎜⎜	DCP	⎜	ISDN-BRI	⎜
	⎜		⎜⎜		⎜		⎜
	⎜ Aggregate Bit Rate		⎜⎜	160 kbps	⎜	192 kbps	⎜
	⎜ Frame Rate		⎜⎜	8 kHz	⎜	8 kHz	⎜
	⎜		⎜⎜		⎜		⎜
	⎜ Bits per Frame		⎜⎜	20	⎜	24	⎜
	⎜ Information Channels		⎜⎜ Two (I1,I2)		⎜ Two (B1,B2)		⎜
	⎜		⎜⎜		⎜		⎜
	⎜ Info Channel Rate		⎜⎜	64 kbps	⎜	64 kbps	⎜
	⎜ Signaling Rate		⎜⎜	8 kbps	⎜	16 kbps	⎜
	⎜ Type Signaling		⎜⎜	Stimulus	⎜	Functional	⎜
	⎜		⎜⎜		⎜		⎜
	⎜ Configuration		⎜⎜	point-to-point	⎜	point-to-point	⎜
	⎜		⎜⎜		⎜	or multipoint	⎜
	⎜		⎜⎜		⎜		⎜