PBL 3852
This axis is the total gain, microphone-telephone-line-telephone station.
This axis is the regulating gain of the speech circuit.
dB
dB
dB
b
c
The point where the
regulation cuts in
can be varied.
The slope of regulation can be
altered in order to compensate
the gain from 0 - P
a
The slope is = q/P
q
a=under comp.
b=opt.comp.
The gain is set on
non regulated value
of the line
c=ower comp.
Line attenuation
approx. center
of the regulation
Area of operation,
given by the network
specification
P/2
Line
km
Regulation area
0
P
Figure 13. Line length regulation.
resistor and if low gain is required it is
connected via a resistor to a level that
is higher than the internal reference of
1.16V. In both cases the current
through the resistor should be ≈ 20 µA
in order to ensure a good precision.
It is possible to combine dynamic
limiting and line length regulation in the
same design as shown in fig. 32. In case
no regulation but high gain is required ,
the pin GR is connected to ground via a
In case no regulation is desired the gain
can be locked either into low or high gain
mode. For high gain mode remove
resistors R14 and R16. For low gain
mode remove resistors R14 and R15.
V
Battery voltage of the system
B (V)
A=1/2 battery feeding resistance
C=cable Ω/km
Is set by 2 A
Is set by 2 A + C P
V Line
V across circ.
V+C
The slope gives regulation
precision
a
b
There must be DC "room" here at the longest specified line
for the supply of the circuit and auxiliary functions.
(Current)
(Line resist.)
Line length km
P
0
Figure 14. The DC-characteristic of a telephone.
10
ERICSSON [ ERICSSON ]
