Siemens SINAUT ST7 - Page 80

Operating Modes and Character Recognition
© Siemens AG 2002 All Rights Reserved 6NH7811-0AA22
MD2 Modem (07/2002)
4-13
Test Operating Mode "Test f
H
"
Similar to "Test f
L
", the "Test f
H
" operating mode 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. 4-8 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. 4-8 the MD2 on the left is a 2-wire terminal point and is set to test operating
mode "Test f
H
" . The MD2 on the right is also a 2-wire terminal point but its
operating mode is set to "Normal".
Fig. 4-8 Test configuration for operating mode "Test f
H
"
In the test operating mode "Test f
H
" the MD2 modem continuously outputs the
upper keying frequency to the WAN port and thus to the 2-wire dedicated line.
The selected operating mode is signaled by the constantly lit "TXD" and "RTS"
LEDs. All other LEDs stay off.
If this upper keying frequency is now correctly received by the opposite MD2, that
MD2 will signalize this by its "RXD" and "DCD" LEDs that both are constantly on. If
the "RXD" and "DCD" LEDs stay off or flash 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
H
"
Operating
mode
"Normal"
LED TXD:
lights constantly
LED RTS:
lights constantly
When receive
level ok:
LED RXD:
lights constantly,
LED DCD:
lights constantly,