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Configuring E1 and T1 Services

117345-B Rev. 00

6-9

Enabling or Disabling CRC

Some E1 equipment expects a 4-byte CRC trailer at the end of each frame.

By default, the CRC trailer is not added to received E1 frames. Set the Line Type

parameter to E1CRC4 if the E1 equipment expects a 4-byte CRC trailer at the end

of each frame.

See the Line Type parameter on page A-12

for information.

Enabling or Disabling High-Density Bipolar Coding (HDB3S)

E1 uses bipolar format for signals. In bipolar format, alternating positive and

negative pulses on the digital line signify the number 1, and the absence of a pulse

signifies 0 (see Figure 6-2 on page 6-4).

A long string of zeros on an E1 line would cause the line to lose synchronization

due to lack of pulses. For synchronization, Bay Networks provides HDB3S, which

is a mechanism to maintain sufficient 1s density in the E1 data stream.

HDB3S support is disabled by default. You can enable or disable HDB3S on this

interface, depending on the ability of the associated E1 equipment to support

HDB3S.

See the HDB3S Support parameter on page A-11

for information.

Setting the Clock Source

The E1 equipment associated with an E1 interface must use a compatible transmit

clock. The E1 interface supports three sources for the transmit clock:

• Internal -- Indicates that the router sets the clock

• Slave -- Indicates that the incoming data stream sets the clock

• Manual -- Indicates that jumpers on the E1 link module set the clock

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Avaya Configuring WAN Line Services Manual do Utilizador Página 111