RAD Data comm HCD-E1 - Manual (Page 33)

HCD-E1 Installation & Operation Manual Chapter 1 - Introduction
01/01/01 08:07 Functional Description 1-15
Table 1-1 Automatically-Selected FIFO Size Values
Data Channel Rate FIFO Size
64 kbps ±16 bits
128 and 192 kbps ±30 bits
256 to 448 kbps ±52 bits
512 to 1536 kbps ±72 bits
1600 to 1792 kbps ±52 bits
1856 and 1920 kbps ±30 bits
1984 and 2048 kbps ±16 bits
Sublink Timing Application
Figure 1-8 shows a typical application which uses the sublink as the timing
reference source, and illustrates the flow of timing signals within the system.
In the application shown in Figure 1-8, a PABX is connected by a HDSL link
to a digital exchange, and must therefore use the exchange timing. For this
purpose, the HCD-E1 unit connected to the exchange uses the clock signal
recovered from the sublink as the system timing reference, and HCD-E1
located on the customer’s premises uses main link timing (LBT).
Therefore, the system timing of HCD-E1 located on the customer's premises
is locked to the digital exchange timing. The exchange timing is thus
transferred to the PABX located on the customer's premises.
Note that the data channels of the two HCD-E1 units must use DCE timing
(or DTE1 timing, provided the data equipment operates with loopback
timing). This enables locking the timing of all the other equipment
connected to the HCD-E1 units to the accurate timing source serving the
digital exchange.