Breakout Box, LEDs, and Connectors B
Advisor Mainframe Features System Guide 63
with existing data signals. In this case, you would want to open
the DTE switch to isolate the circuit being tested from the
internal data transmitter.
In monitor mode, the inputs to all V-Series signal receivers
represent only 1/5 of a standard load, minimizing circuit
loading effects. In Simulating and BERT testing modes, the
transmitters are configured with normal source impedance.
Mark/Space Indicator
You can use the Mark/Space Indicator to test the state of any
circuit on an RS-232/V.24 interface. The Mark/Space Indicator
has two test jacks, which are connected together electrically. To
do this, simply jumper from any test jack on either of the lateral
or vertical switch banks to either of the Mark/Space Indicator
jacks and observe the results. If the incoming signal is more
positive than +3.0 volts, the Space LED lights. If the incoming
signal is more negative than -3.0 volts, the Mark LED lights. If
the Mark and the Space LEDs both light up, the incoming signal
is actively changing states. This is normal for data and clock
signals, but indicates a problem for control signals.
Pin 1 of the RS-232 test port is Frame Ground or Protective Ground. It is
connected to the case of the Advisor and, through the third wire of the
power cable, to Ground. If you have a data circuit that requires isolation of
Frame Ground, use the forward RS-232 test port and open switch 1 on the
lateral switch bank
Pin 7 of the rearward RS-232 test port is Signal Ground, and it is isolated
from Frame Ground by 100 KOhms to minimize ground-loop problems.
EIA-232D (Formerly RS-232C) specifications consider interface signals in
the range of -3.0 to +3.0 volts to be indeterminate (or not valid). Consistent
with this recommendation, the Mark/Space Indicator treats signals in this
range as “not present” and gives no indication.
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