Operating Modes and Character Recognition
© Siemens AG 2002 All Rights Reserved 6NH7811-0AA22
MD2 Modem (07/2002)
4-11
Test Operating Mode "Test f
L
"
The test operating mode "Test f
L
" can be used to determine the quality of a 2-wire
or 4-wire dedicated line by measuring the attenuation characteristics in relation to
the baud rate.
Fig. 4-6 shows one possible test configuration for a point-to-point connection with
2-wire half-duplex. This could also be a multidrop or star network. Any other
network type using 4-wire full-duplex could also be tested.
In Fig. 4-6 the MD2 on the left is a 2-wire terminal point and is set to test operating
mode "Test f
L
". The MD2 on the right is also a 2-wire terminal point but its
operating mode is set to "Normal".
Fig. 4-6 Test configuration for operating mode "Test f
L
"
In the test operating mode "Test f
L
" the MD2 modem continuously outputs the
lower keying frequency to the WAN port and thus to the 2-wire dedicated line.
The selected operating mode is signaled by the constantly lit "RTS" LED. All other
LEDs stay off.
If this lower keying frequency is now correctly received by the opposite MD2, that
MD2 will signalize this by its "DCD" LED that is constantly on. If the "DCD" LED
stays off or flashes irregularly; then this indicates an incorrect data reception. For
possible causes: see section Possible Error Causes.
LTOP1
overvoltage
protection
6NH9821-0BC11
LTOP1LTOP1
LTOP1
overvoltage
protection
6NH9821-0BC11
2-wire dedicated line
MD2
MD2
Cable
6NH7700-2AR60
Cable
6NH7700-2AR60
Operating
mode
"Test f
L
"
Operating
mode
"Normal"
LED RTS:
lights
constantly
when
receive
level ok:
LED DCD:
lights
constantly
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