2.4.3.4 T1/E1 External Reference Timing
The T1/E1 external reference timing is provided by a TSICOM.
For synchronization with the network, an external timing source should be connected
to the TSICOM. The source can either be the incoming digital trunks, or a BITS box,
if so equipped. Without proper synchronization, timing slips may occur leading to
digital facilities being taken out of service.
Table 2-3 — TSICOM External Timing Reference Cables
Cable Type Application
G454 Links TSICOM (UM74C) to a BITS clock or DSX Bridging
Repeater. Non-EMC, 24 channels, 100 ohms, 0.772 Mb/s.
(References ED5D675-17 G26 and G27 for the actual cables for
Side 0 and Side 1).
G455 Same as G454 but with EMC treatment .
The cable used to connect the external clock reference to the SM-2000 is ordered from
ED5D500-21 (see Figure 5.11-1). Depending on the application, one of the cable types
from Table 2-3 must be ordered.
2.4.3.5 Digital Service Control Unit
The Digital Service Control (DSC) provides the tone generation (for example, audible
ring and dial tone) and tone decoding (for example, digit interpretation) functions
required by every switching module.
2.4.3.6 Peripheral Units (PUs)
Peripheral Units (PUs) are those units that are engineered into the switching module
to meet the needs of the customers. Optional PUs include:
• Line Unit 3 (LU3) - provides the termination of up to 640 analog lines capable of
providing 4:1, 6:1, 8:1 and 10:1 line concentration.
• Digital Network Unit - Sonet (DNU-S) - provides termination of trunks.
• Digital Service Unit 3 (DSU3) - provides Recorded Announcement Functions
(RAF), Integrated Services Test Functions (ISTF), and Voice Path Assurance
(VPA).
• Digital Line and Trunk Unit 2 (DLTU2) - provides termination for T1 digital
trunk facilities.
• Modular Metallic Service Unit (MMSU) - provides access to perform metallic
testing of lines and trunks and provides miscellaneous scan and distribute points.
• Global Digital Service Function (GDSF) - provides transmission test functions
and conference circuits.
• Integrated Digital Carrier Unit (IDCU) - provides termination of the following
Digital Service (DS) facilities:
— TR08 SLC
®
96 SLC Series 5 FPB SLC Access System
— TR303 SLC Series 5 FP303 SLC Access System Release 4 (Nov 94)
— PUB43801 D4/D5 DACS II
5ESS
®
SWITCH DISTINCTIVE REMOTE MODULE 235-200-150
Feburary 2007
Page 2-12 Issue 3.00O
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