PBL3852 查看數據表（PDF） - Ericsson

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PBL3852

Universal Transmission Circuit

Ericsson  

PBL 3852

This axis is the total gain, microphone-telephone-line-telephone station.

dB

This axis is the regulating gain of the speech circuit.

dB

b

dB

c

The slope is = q/P a

q

The slope of regulation can be

altered in order to compensate

the gain from 0 - P

The point where the

regulation cuts in

can be varied.

a=under comp.

b=opt.comp.

c=ower comp.

The gain is set on

non regulated value

of the line

approx. center

of the regulation

P/2

Line attenuation

Area of operation,

given by the network

specification

Regulation area

0

P

Line

km

Figure 13. Line length regulation.

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.

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

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.

V

B (V)

Battery voltage of the system

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.

P

0

Figure 14. The DC-characteristic of a telephone.

10

(Current)

(Line resist.)

Line length km

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