Unit installation

Installation and Operation Manual Chapter 1 Introduction

FCD-E1 Functional Description 1-17

FCD-E1/S1

PBX

(Loopback Timing)

DCE

Timing

Sublink

Timing

Data

Channel

DCE

Timing

Digital

Exchange

Sublink

User's DTE

Network

Data

Channel

Customer Premises

Figure 1-5. Sublink Timing, Flow of Timing Signals in a Typical Application

In the application shown in Figure 1-5, a PBX is connected by a fractional E1 trunk

to a digital exchange, and must therefore use the exchange timing. For this

purpose, the FCD-E1/S1 connected to the exchange uses the clock signal

recovered from the sublink as the system timing reference, and the FCD-E1/S1

located on the customer’s premises uses main link timing.

Therefore, the system timing of the FCD-E1/S1 located on the customer’s premises

is locked to the digital exchange timing. The exchange timing is thus transferred to

the PBX located on the customer’s premises.

Note that the data channels of the two FCD-E1 units must use DCE timing (or

DTE1 timing, provided the user’s equipment operates with loopback timing). This

enables locking the timing of all the other equipment connected to the FCD-E1

units to the accurate timing source serving the digital exchange.

Data Channel Timing Application

Figure 1-6 shows a typical application which uses one of the data channels

operating in the DTE2 timing mode, as the timing reference source, and illustrates

the flow of timing signals within the system.