User Manual

2240 Fiber Optic Modem

This interface performs jitter attenuation of the transmit line input signal. It is also

designed to propagate an all "1's" AMI stream if the end-to-end line is interrupted at

any point.

When using any of the Transparent Bipolar Interfaces, the 2240 modem rate and

mode front panel DIP switches should be set as follows: 1-4 = closed, 5-7 = open

(Rate 0, Mode 7). In addition, the first two positions of the internal DIP switch S1

must be:

CD / DCD = OFF and CD / SYNC = ON. Refer to Section 2.2.2.1.

If the interface signal is lost, Loss of Signal (LOS), the all "1's" Alarm Indication

Signal (AIS) is sent to the other end.

Factory Setting = Both jumpers are OFF

These interfaces allow full inter-operation with any of the synchronous data inter-

faces when the customer's T1/E1 is AMI-coded (see Figure 4-3). This interface will

not inter-operate with synchronous data interfaces if the T1 / E1 is B8ZS or HDB3.

Two jumper straps are provided for setting the line termination impedance to either

100 ohm for T1 or 120 ohm for E1 applications. These straps are located near the

middle of the interface board and are provided only for the 4B1 and 4B2 versions.

For the 4B3 version (BNC connectors) the termination impedance is fixed at

75ohms.

Table 4-N.

Transparent

Bipolar Line

Interfaces

Model # Interface Speed

Connector

Type

4B1 DA-15 1.544 Mhz T1 or 2.048 Mhz E1

4B2 Terminal Block 1.544 Mhz T1 or 2.048 Mhz E1

4B3 BNC (75 ohm) 1.544 Mhz T1 or 2.048 Mhz E1

These interfaces are fully transparent to line codes such as B8ZS or HDB3.

Three DIP switches (3, 4 and 5) are provided for selecting various line build

out settings as indicated in Table 4-M. Standard factory settings are T1 at

0-133 feet for all three models. Two DIP switches (1 and 2) are provided to

select CCITT speed (2.048 Mhz) or T1 speed (1.544 Mhz).