Black Box ME475A-R2, Manual

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Operation
4. OPERATION
4.1 LED STATUS MONITORS
The ME475A-R2 features six front panel status LED that indicate the condition of the
modem and communication link. Figure 6 shows the front panel location of each LED.
Following Figure 6 is a description of each LED’s function.
Figure 6.
Front view of ME475A-R2
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.
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.
The “Test” Indicator
The green “Test” LED indicates that V.52 or V.54 tests are running.