AT&T 7300 series, 7500 series, 7100 series, 2500 series, 7200 series Exiting the Switch, ⎜ Module

TRANSMISSION STATES 1-9

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∙Incoming digital-trunk calls to a digital switch need no conversion since the call is already PCM encoded. Incoming digital-trunk calls to analog switches are converted outside the switch at a D4 channel bank. In these cases, the digital trunk terminates at the D4 channel bank. From the D4 channel bank, incoming calls are forwarded to the switch via analog trunks. (See Multiplexed Communication later in this chapter.)

Inside a digital switch, therefore, voice is always coded as PCM. Inside an analog switch, voice is coded as PAM for time-multiplexed switches or left as a pure analog signal for matrix switches.

Below is a table that summarizes the types of signals that particular terminals generate and the types of circuit packs that can handle the signals.

Table 1-1.Terminal/Port Compatibility

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⎜

⎜

⎜

Circuit Packs

⎜

⎜

⎜

⎜

⎜

⎜

⎜

___________________________________________________________

⎜

⎜

⎜

⎜

⎜

⎜

Terminal

⎜

Signal

⎜

Type

S75/G1

S85/G2

⎜

⎜

DIMENSION

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

______________________

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜ Traditional

⎜

⎜

⎜

⎜

⎜ Universal

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜ Module

Module*

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

2500 series

Analog

Analog

⎜

LC02

⎜ TN742

⎜ SN229

⎜ TN742

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

7100 series

⎜

N/A

⎜

TN742

⎜

SN229

TN742

⎜

⎜ Analog

⎜ Analog

⎜

_

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜ 7200 series

⎜ Analog

⎜ MFET

⎜

LC02 & LC55

⎜ TN735

⎜ SN224

N/A

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

7300 series

Analog

MFAT

⎜

N/A

⎜ TN762

⎜ ANN17

⎜ TN762B

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜ 7400 series

⎜ Digital

⎜ Digital-line

N/A

TN754

SN270

⎜ TN754

⎜

⎜

⎜

⎜

⎜

⎜

⎜ or GPP

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

7500 series

Digital

BRI

⎜

N/A

⎜ N/A

⎜ N/A

TN556

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

⎜

* Universal modules are available only on the G2 switch.

Note that the table names the circuit-pack type by the type of terminal that can use it. Multifunction electronic telephones use MFET circuit boards; multifunction analog telephones use MFAT circuit boards; DCP terminals use digital ports (called digital-line ports on the S75/G1, and general-purpose ports [GPP] on the S85/G2) and basic rate interface terminals use BRI ports.

To complete the picture of analog and digital switch ports, you also need to know the trunk port types, names, and numbers given in figure 1-2.(See the Trunking section of this chapter for an explanation of trunk types and protocols.)

Exiting the Switch

For outgoing or tandem calls that are routed over analog trunks, and for intercom or incoming calls to analog telephone sets, another conversion must occur.