5.1.4 The “Error” Indicators
The “Error” indicator LED has three functions:
A. When the 1080A Series unit is in test mode (green “Test” LED is
lit), the error LED glows red when bit errors occur.
B. When not in test mode (green “Test” LEDis off), the error LED is
used to indicate an RTS streaming condition. (See Section 5.2) for
information on the anti-streaming circuitry.
C. The “Error” LED is also used to detect line quality, such:
1. The improper use of flat (non-twisted pair) cable to connect
the modems.
2. One or more broken wire in the 4 wire twisted pair cable.
3. The use of low quality twisted pair cable to connect the
modems.
4. Broken or corroded connector.
NOTE: In detecting line quality the “Error” LED indicator is designed for
4 wire twisted pair cable only, and may not function properly with two
wire cable.
5.1.4.1 Setting Up The “Error” LED To Test Cable Quality
If there is any question as to the quality of your line we recommend
the following test:
1. Disconnect both local and remote modems from their RS-232
interface. Make sure “TD”, “RD” and “RTS” LEDs are lit red.
2. Set input impedance of both modems to 200Ω. (S3-1 “On”,
S3-2 “Off”). NOTE: When testing Model 1080A-64, use
22AWG, 24AWG, or 26AWG cable only,
3. For Model 1080A, set data rate on both modems for9.6kbps
For Model 1080A-64, set data rate on both modems at 16
kbps.
4. On local modem set “Carrier Constantly On”. (S1-8 “Off”)
5. Set remote modem to RTS control (S1-8, “On”).
6. Place both front panel toggle switches to neutral position.
(Test Led will not light)
7. Connect both modems to the 4 wire twisted pair cable.
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5.0 OPERATION
Once you have configured each Model 1080A Series unit properly
and connected the twisted pair and RS-232 cables (see Section 4.0),
you are ready to operate the units. This section describes reading the
LED status monitors, powering-up and using the built-in V.52 and V.54
test modes.
5.1 LED STATUS MONITORS
The Model 1080A Series features six front panel status LEDs that
indicate the condition of the modem and communication link. Figure 5
shows the front panel location of each LED. Following Figure 5 is a
description of each LED's function.
5.1.1 The “TD” and “RD” Indicators
The “TD” and “RD” indicators blink red and green with data activity.
Red indicates a low RS-232 logic level, green indicates a high RS-232
logic level. Note: RS-232 devices idle in a
low
state, so the LED will
glow red if the connections are correct and the RS-232 device is in an
idle state.
5.1.2 The “RTS” and “CD” Indicators
The “RTS” and “CD” indicators are bi-color and will glow red for a
“low” signal or green for a “high” signal. RTS lights for an incoming
signal on RS-232 pin 4. CD lights for an incoming signal on the line
side, and the resulting output signal on RS-232 pin 8.
5.1.3 The “Test” Indicator
The green “Test” LED indicates that V.52 or V.54 tests are running.
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Figure 5. Front view of Model 1080A Series
Model 1080 Universal Short Range Modem
TD RD RTS CD
V.54 Test
Modes
Remote
Normal
Local
Error Test
511
511E