Determination Of The Receive Level - Siemens SINAUT ST7 Operating Instructions Manual

2.2.7

Determination of the receive level

To determine the receive level the MD2 modem at the beginning of the dedicated
line must be set to the test operating mode "Test f
page 2-15). This modem will then continuously send the upper keying frequency of
the selected baud rate (see Table 2-20) on the dedicated line. After this the level
available at the other end of the dedicated line can be checked there. If this
dedicated line is a line with several tapping points, then all of these tapping points
must be included in the line (incl. LTOPs) to achieve a correct measurement.
Note
For level measurements it is important to ensure that the line termination is set to
150 Ohm (for 9600 / 19200 bps) or 600 Ohm (for 1200 / 2400 bps) at a terminal
point or 6 kOhm at a tapping point. It is also important to carry out the
measurement without grounding since the dedicated line operates with a
symmetrical signal.
The MD2 modem can receive data up to a minimum level of –43 dB. What level is
actually available at the receiving end must be verified with an appropriate
measuring device. If this is not available, the level still may be determined with
adequate precision using a normal voltage measuring device. For this purpose the
following table summarizes the level values and the assigned voltage values (U
AC voltage).
Table 2-23
Level
+10 dB
0 dB
-3 dB
-6 dB
-9 dB
© Siemens AG 2002 All Rights Reserved
MD2 Modem (07/2002)
Comparison of level and voltage values
Voltage
Level
value (AC)
2,45 V -10 dB
775 mV -12 dB
552 mV -15 dB
389 mV -18 dB
274 mV -20 dB
Mounting and Installation
" (see Table 2-13,
H constant
Voltage
Level
value (AC)
245 mV -25 dB
195 mV -30 dB
137 mV -35 dB
97,8 mV -40 dB
77,7 mV -43 dB
rms
Voltage
value (AC)
43,5 mV
24,5 mV
13,7 mV
7,8 mV
5,5 mV
6NH7811-0AA22
2-31