Specifications

CHAPTER 2: Introduction

2.4.4 LOCAL AGGREGATE LOOPBACK

The LOCAL AGGREGATE LOOPBACK diagnostic (Figure 2-4) enables the user to verify the T1

CSU/DSU logic from the channel interface, through the aggregate, and return to the channel interface.

To select this test, position the AGGREGATE LOOPBACK switch in the LOCAL position. When

complete, reposition the switch to the center position.

Figure 2-4. Local Aggregate Loopback.

2.5 NETWORK LEDs

Six LEDs indicate network function of the unit: Loss Of Signal (LOS), Bipolar Violations (BPV),

RED and YELLOW alarms, SYNC, and TEST.

LOS LED — when illuminated, indicates the lack of sufficient signal pulses(marks) at the network receiver. The LED

is illuminated when more than 175 consecutive zeros are received and is extinguished when the next mark is detected.

Bipolar Violations LED — when illuminated, indicates that a pulse was received that is of the same polarity as

the preceding pulse(excluding B8ZS codewords), thus violating the Alternative Mark Inversion Rule.

RED ALARM LED — illuminated when the receiver has lost frame synchronization for 2 to 2.5 seconds.

The LED is extinguished when FRAME SYNC has been acquired for at least eight consecutive seconds.

YELLOW ALARM LED — illuminated while a YELLOW ALARM indication is being received from the remote unit.

The remote unit will transmit a YELLOW ALARM indication while in the RED ALARM state. While operating in D4 framing,

the YELLOW ALARM condition is transmitted by forcing bit 2 of every DS0 to a zero state. In ESF framing mode, the YELLOW

ALARM condition is a pattern embedded in the framing overhead.

SYNC LED — lit when the local unit is in SYNC with the remote unit. It is extinguished when

synchronization is lost. Frame sync criteria is the receipt of 10 consecutive F bits. Sync loss criteria

is receipt of 2 of 4 consecutive frame word errors.

TEST LED — lit whenever the unit is in a selected diagnostic mode or test ,or while the unit is sending

diagnostic patterns.

2.6 CHANNEL LEDs

The four LEDs below the CHANNEL heading represent the status of the channel side of the unit.

The Channel TD (green) LED is illuminated when the channel is transmitting a space. The Channel RD

(green) LED is illuminated when the channel is receiving a space. The Request to Send (RTS) LED is

illuminated when the Request to Send function is active. The Channel RLSD (green) LED is illuminated

when the channel’s Receive Line Signal Detect function is active.

2.7 REAR PANEL CONTROLS AND INTERFACE CONNECTORS

The rear panel (Fig. 2-5) provides access to the physical interfaces necessary to connect the unit to a

network. Depending on the model, there is one of the following female connectors on the rear panel

for the DTE interface: 34-pin M block (V.35); DB37 (RS-449); or DB25 (RS-530). There is also a five-pin

DIN power connector for applying logic power (–5 and +/–12 VDC) to the unit. There are two DIP

switches—Switch 1 and Switch 3—along with the LBO switch (Switch 2).

Test

Equip.

CHANNEL CHANNEL