PSB2132 Datasheet, PDF (78/95 Pages) Siemens Semiconductor Group – Two Channel Codec Filter for Terminal Applications SICOFI2-TE

PSB 2132
PSB 2134
Application Note: Level Metering
To calculate the applied analog level, the gain settings of the SICOFI2/4-TE filters
together with the 0 dBm0 reference voltage have to be taken into consideration.
Analog
Test Signal
~
C _VIN
GNDA
Figure 34
Measurement of an unknown level
Level Metering
Function
SICOFI2/4-TE
8.9 Loops
If the test signal is fed via tone generator 1 or via PCM4 in the receive path of the
SICOFI2/4-TE a loop is necessary to feed the test signal back to the transmit path.
Digital loops are implemented in the SICOFI2/4-TE and can be activated by writing
register CR4. After switching an internal loop the measured level is a representation of
the internal attenuation and amplification via the filter blocks. Such self tests show
whether the SICOFI2/4-TE is working or not and how it is adjusted.
In a line card application a SLIC is connected to each channel of the SICOFI2/4-TE. The
SLIC together with a connected analog telephone creates a loop from the receive-path
to the transmit path. SLIC, subscriber line and telephone have a special impedance
according to their specification. If only one of them changes the value, the returned test
signal will be changed und will indicate a change in the corresponding system condition.
Therefore, changes of the telephone state, the subscriber line length or the SLIC can be
supervised.
8.10 Application Examples
8.10.1 Supervision the State of a Subscriber Line
The configuration of an application example is shown in figure 38.
tip _{TAS 2100}
ring ^{Loop Emulator}
Analog
Telephone
Set
Subscriber Line
tip
Harris-SLIC
ring
HC3-5502B
SLIC
VIN
VOUT
Level Metering
Function
Test Signal
Tone Generator 1
SICOFI2/4-TE
Figure 35
Test configuration
Semiconductor Group
78
09.97