DE1804745C3 - Circuit arrangement for adapting the impedance of a telephone device to the characteristic impedance of a subscriber line - Google Patents

Description

tragers directly parallel-connected capacitor as well as a resistor or egg.ien capacitor, which are connected to the line terminals [a, b) , contains (Fig. 8 and 9).

transformer of the apparatus in series with a capacitor upstream all-pass. This all-pass network is designed so that the resulting

The invention relates to a circuit arrangement
to adjust the impedance of a one
Circuit with a transmitter containing telephone device to the characteristic impedance of a part _... _a

, subscriber line with a matching circuit, the ₄₅ reflections at the connection point between apparatus

contains a capacitor and is so dimensioned, and known line, which consists of one of the speech

that the minimum of the curve which corresponds to the course of the imaginary part of the apparent resistance of the

Switching of the telephony device as a function of

corresponds to the frequency, in the upper part of the remote ₅ o impedance (apparatus + Isletzwerk) within a

Speaking frequency range. essential part of the frequency band capacitive

Investigations of the behavior of the line connected in one and equal to the imaginary impedance of the circuits contained in the subscriber telephone set apparatus. The inductances necessary for the show that such circuits are essentially all-pass are relatively inductive. The impedance of such agile components, which moreover only has a real and an imaginary part after switching off, has an existing connection between the value and always increases with increasing frequency
- remains positive.

In contrast to this, the behavior of the subscriber lines used in general ■ is in wcsent-no
borrowed capacitive. The impedance of the line
has a positive real part, which decreases with increasing frequency and approaches a constant limit value, and a negative imaginary part, its
The absolute amount can also become 65 with increasing frequency, decreases. Dis invention consists in that without use

The apparent resistances of the device circuit and a matching inductance create a series or parder Subscriber line can obviously connect from one capacitor and one

Speech transformer and an input terminal or the earpiece built into the subscriber circuit can be.

The object of the invention is to provide a matching circuit of the type mentioned above, which is less complex than the known correction network described above and also simply connected to a subscriber circuit

Resistance between the terminals of the line and / or a capacitor is connected in parallel to at least one winding of the transformer .

An adaptation or compensation circuit according to the invention is therefore always a simple KC-NeIzvverk, in which the conductance of the resistor is also Can be zero or infinity and which is not in series, but only in parallel with the subscriber circuit or parts thereof.

The compensation circuit is dimensioned as follows: If the transmitter can be regarded as ideal, the compensation circuit of the call station and the subscriber line are independent of one another, and therefore no current flows in the compensation circuit when a tone frequency signal arrives from the line, which are therefore considered to be non-existent can. In practice, this requirement is met with a good approximation.
; Based on the assumption made, the impedance Z of the telephone equipment sound can be represented by the following formula:

(1)

mean thereby

L _r inductance of the listener,
R _r resistance of the listener,
L leakage inductance of the transformer,
R _m microphone resistance,
μ = 2π / the angular frequency of the audio frequency signal.

The above formula shows that the real part P _{r of} the impedance Z, starting from the value R _1n for ω = 0 with increasing frequency, increases and becomes the value for ω- * · χ

J ** '+ R

the impedance of the circuit as follows; The conductance is obtained from Z ~ P _r + JP ₁ , in which P 1 and P _{1 have} the values determined by the equation Πι

p _r

or, the Blindlcitwcrt

^L - i * + pV

the entire admissions of the circuit becomes
Y = H ₁ G + Jd ₁₁ C ₁ -E),

from this one obtains the impedance by inserting D ~ g, + Q

7 ^{l D} -J ¹ ^ i -JQ n \

¹ D + HmC ₁ -E) W + (,., C ", '-"^'^l>

the real part

approaches, while the imaginary part P ₁ approaches from the value 0 for μ = 0 to the value oo for n> - * oo and always remains positive.

The impedance of the circuit of the telephone set is always opposite to that of the line.

The values of the circuit parameters of a compensation circuit comprising a capacitor and a Resistance cnthäSt, which are connected in parallel to the line, must in view of the following Principles are chosen that approximate the behavior of the telephone circuitry to the of the line within the telephone frequency range enable, at least for the area in which the flow is more important in practice the line predominates. These design principles must be of the formula (1), which defines the line-side impedance the telephone circuit indicates, take into account.

If a resistor R ₁ with the conductance G, = I / R, and a capacitor with the capacitance C ₁ corresponding to the capacitive susceptance at C _{1 are connected in} parallel to the telephone device circuit, it changes

and the imaginary part

D ² '+' (mc, -E) ²

The real part is equal to IJD for ω = 0, and for to - * 00 it strives for O; it has a minimum for an «j value determined _{by the values g 1} and C 1.

The imaginary part is for ω = 0 and for ω - EIC-,

equals 0 and has a maximum in between. After

the second zero the imaginary part passes through a minimum and then strives for 0 for m - * 00.

The values of the resistor and the capacitor, which are to be connected in parallel with the line, should be chosen so that the minimum (maximum value of the absolute value) of the imaginary part coincides with the upper limit of the telephony frequency band. If the imaginary part is to have the value - H for a certain frequency, then the value is obtained for the capacitance to be used

fi-4H ² D ²

2 Hin

This equation only has for

a solution. _

When the imaginary part reaches the minimum value - H , the term under the square root of the above expression becomes 0. After defining - Ή , the condition is obtained from this

The conductance g and the capacitance C ₁ -, which are to be connected in parallel to the line, are then obtained immediately:

Hi ₁ means the angular frequency at the upper limit of the telephone frequency band.

The condition D = Iβ H also leads to the result that the absolute values of the real and imaginary parts of the impedance of the telephone circuit are the same at the upper limit of the telephone frequency band, and a typical characteristic of the characteristic of the characteristic impedance of the subscriber line is simulated.

The values of the circuit elements of a compensation circuit which includes one or more capacitors connected to only one winding of the transformer are selected according to the following principles which ensure that the behavior of the telephone circuit will approximate that of the line within the most interesting range of the telephone frequency band. The design rules η again depend on the above formula (1). The connection of a capacitor to one of the windings of the transmitter means that this capacitor is parallel to the sound system containing the transmitter and the receiver and that the microphone resistor R _{1n is} connected in series with this parallel connection.

Conversion gives

and one determines the conductance as well as the blind value the telephone circuit without the microphone, of course

P '

^{G / =} p; ¹ + ^

F- '

the following equation is obtained for the impedance Z _{2 of} the circuit, in which C means the capacitance of the connected capacitor

G ₁ -ji'oC, -E ₁ )

^K m <

who has the following real and imaginary citations

ρ

rl

G ₁

l ι η

i- E, f

The best match is obtained when the minimum is at the upper limit of the telephony range Cherishes.

According to these principles, the capacity of the parallel capacitor can be determined. If the angular frequency is set at the upper limit of the radio frequency range equal to M ₁ , then m ₂ = (E ₁ + G ₁ ) C ₁ , and from this the value for C ₁ follows:

_r _ E _x -VG ₂

'"2

(10)

The callcil for ω = 0 is equal to R _m , has a maximum for m = C ₁ / Cj and strives for R _1n for m- * <x> . The imaginary part is zero for> = 0, then becomes positive, if ω = EJC ₁ again zero, with a maximum occurring in a middle point, then becomes negative, has for m - (E, + G ₁ ) JC ₁ a Minimum and finally strives for zero for m -> co.

The two compensation noises described can be equivalent in different ways will be realized. The first compensation circuit can have one connected to the input of the line Reduce the capacitor, in this case the compensation resistor has an infinite value great value, d. H. g, = 0. You can also use a series circuit of a capacitor and a resistor use; another option is to have a resistor and a first one Capacitor existing parallel circuit, to which a second capacitor is connected in series, to be used. There are also other equivalent ones

Circuit arrangements.

The second type of compensation circuit can be either a capacitor or combinations of capacitors and resistors, which are connected to several windings connected in series

lungs are connected.

Impedance measurements have also approved. that you get good results even with circuit arrangements obtained from combinations of the two types of compensation circuit

gen exist. So you can z. B. a compensation circuit with a to a winding of the transformer connected capacitor and a capacitor connected to the input of the line and one connected to a winding

Capacitor and a resistor connected to the input of the line or a capacitor connected to the winding of the transformer and one from gtps » _m \ wa ~ ·. 1 .4 * ,; _n om

Capacitor existing, at the input of the line

use connected series connection.

The invention is explained in more detail below with reference to the drawing, it shows

Figure 1 shows a typical telephone set circuit as well as a graphic representation of the real and

Imaginary part of the apparent resistance of this circuit as well as the wave resistances of two different ones common subscriber lines,

Figures 2, 3, 4 and 5 each show a telephone set with a compensation according to the invention

Sation circuit of the first type, as well as a diagram of the impedance of the circuit and two typical lines,

F i g. 6 and 7 each a telephone device circuit with a compensation circuit according to the invention

development of the second type as well as a diagram of the impedance of the circuit and the characteristic impedance from two typical subscriber lines,

Figures 8, 9 and 10 each show a telephone set with a compensation according to the

sation circuit resulting from a combination of the two types mentioned above, and a diagram the apparent resistance of the circuit and the characteristic impedance of two lines.

The in F ί g. 1 includes a transformer with three windings, of which the winding I is connected to a telephone line terminal α and via a microphone M to a telephone line terminal b . winding II is connected to a receiver T and winding III is connected to a terminating circuit B consisting of ohmic resistances and reactances, which usually contains a resistor or a resistor with a capacitor.

In the one shown in FIG. 1, as in the diagrams of the other figures, the impedance in ohms is plotted along the ordinate and the frequency in kHz is plotted along the abscissa. The curves R ₀ and jX _a give the course of the real or. Imaginary part of the apparent resistance of the above-mentioned telephone equipment sound, while the curves 1, Γ the real or imaginary part of the wall contradicting a subscriber line with wires that have a diameter of 0.4 mm, and the curves 2.2 'the course of the real or imaginary parts of the wave contradiction of a subscriber line, the wires of which have a diameter of 0.6 mm.

It can be seen that the real and imaginary parts of the thermal resistance of the lines increase with Frequency decrease in magnitude and the imaginary parts are negative, while the real part is the impedance the telephone circuit becomes larger with the frequency and the imaginary part slowly decreases, but always remains positive.

The in F i g. 2 as ais Ausführungsbeispicl of the invention includes the telephone device circuit shown in the description of the circuit according to FIG. 1 circuit elements already mentioned, a resistor R _f and a capacitor C ₁ , which are connected in parallel to the line terminals a, h. The curves in FIG. 2 has the same meaning as in FIG. 1. From the in F i g. 2 it can be seen that the real part R _{0 of} the device circuit decreases after passing through a maximum value of about 640 ohms at about 680 Hz and lies between the values of the real parts of the two lines under consideration, while the imaginary part after the zero crossing is always negative at about 680 Hz remains and gradually approaches that of the lines.

In the circuit according to FIG. 3, the compensation circuit is limited to a capacitor C ₁ .

From the in F i g. 3 it can be seen that the curve R _a representing the real part of the impedance of the device circuit occurs at about 560 Hz between the curves 1, 2 corresponding to the real parts of the thermal resistance of the lines and runs in most of the remaining frequency band between these two curves, while the curve j X ₁₁ representing the imaginary part of the device circuit passes through zero at approximately 720 Hz and then approaches the curves 2 ′ and Γ representing the imaginary parts of the characteristic impedance of the lines.

In the circuit according to FIG. 4, a resistor R and a capacitor C connected in series with the latter are connected to the terminals a, b of the line. _{The associated diagram shows that the curve R 0} representing the real part of the impedance of the device circuit occurs at around 560 Hz between the curves 1, 2 representing the real parts of the characteristic impedance of the lines and that the imaginary part jX _a becomes zero at around 800 Hz and is then approaches the imaginary levels 2 'and Γ of the wave impedance of the lines.

In the embodiment according to FIG. 5 is to the line terminals a, b from a capacitor C "

ίο and a resistor R ₍ existing parallel circuit, which a capacitor C ₁₂ is connected in series, connected.

The corresponding diagram shows a very good correspondence between the curves of the real part R _{11 of} the impedance of the device circuit and the real parts 1, 2 of the wave impedance of the lines, as well as a satisfactory behavior of the imaginary part jX _{a of} the device apparent resistance, which becomes zero at around 600 Hz and then always negative remains.

zo In the embodiment according to FIG. 6 is the Winding I of the transformer is a capacitor C, connected in parallel.

The associated diagram shows that the real part R _{11 of} the impedance of the device circuit

at about 550 Hz the values of the real parts 1, 2 of the wave resistance of the lines reached and then in the rest of the telephone frequency range always keeps in the vicinity of these values, while the imaginary part the impedance goes through zero at about 800 Hz and then door the remainder of the telephone frequency band always remains negative.

In the embodiment according to FIG. 7, which represents a modification of the exemplary embodiment according to FIG. 1, the capacitor C _{1 is} connected in parallel to the two windings I, III.

The associated diagram is similar to that of FIG. 6, the course of the imaginary part jX _a , which goes through zero at around 700 Hz, is somewhat more favorable.
The in Fig. The embodiment of the invention shown in FIG. 8 is based on a combination of the two types of compensation circuits described above, since a first capacitor C _{n is connected} to winding I and a second capacitor C _{n is connected} to line core a, b ,

The exemplary embodiment according to FIG. 9 also corresponds to a combination of the two types of compensation circuits, since a capacitor C _{1 is connected} to winding I of the transformer and a resistor R 1 is connected to the line terminals a, b.

The embodiment according to FIG. 10 also corresponds to a combination of the two types of compensation circuits, since a first capacitor C _{11 is connected} to winding 1 and a series circuit consisting of a resistor R ₁ and a second capacitor C _{12 is} connected to line terminals a, h.

_{The associated diagram shows that the curve R 0} representing the real part of the impedance of the device circuit from about 550 Hz between the

• 60 curves representing real parts of the wave resistance of the lines runs, while the curve jX " representing the imaginary part of the impedance of the device circuit" passes through zero at about 600 Hz and then with increasing frequency the imaginary

dividing the wave resistances of the lines approaching.

In addition 5 sheets of drawings

709 615/82

./>, V``ir (■ "fy. ¹

j _t

Claims (3)

Patent claims: I. Circuit arrangement for adaptation dc » Seheinwiderlandes a cine circuit with a transmitter containing telephony device to the characteristic impedance of a subscriber line with a matching circuit containing a capacitor contains and is dimensioned in such a way that the never become the same because of their fundamentally different behavior. If the remote control device with the associated The trunk connecting the trunk is short (e.g. about 100 m). can influence the leadership on the office-side Impedance of the line and telephone device are practically neglected, whereas with long Lines (longer than 2 km) the influence of the line predominates and consequently the arnt-side illusion j h d Abtd wishen d F Minimum of the curve which the course of the Ima-, 0 resistance depending on the distance between the remote primary part of the apparent resistance of the adapted speech device and the associated office of the value of the circuit of the telephone set as a function of
corresponds to the frequency, in the upper part of the Telephone frequency range is, thereby Telephone device circuit up to which the line changes. Attempts have already been made to gck en η draws η et that without using 15 differentiation of the apparent resistances resulting after adjustment Adaptation induction to avoid a series or 'split through the use of listeners, which have an impedance that is as frequency-independent as possible. When using such Handset has the impedance of the telephone Parallel sound from a capacitor (C ,, C _n , C _n ) and a resistor (R ₁ ) between the terminals («, b) of the line and / or a capacitor (C ₁ , C _n ) parallel to at least one winding of the device circuit, a real part, which is connected almost constantly to the transformer. is. while the imaginary part has a small and nearly has a constant value that always remains positive. It is also known between the telephone set and the subscriber line one of a stood (R ₁ ) a first capacitor (C ₁₁ ), so-called »afterimages a second capacitor (C ₁₂ ) in series generation line« to 25 passive four-pole existing ones, the effect of which with the. "ui- <: -" .. . * ■. ..j ,, ..., a few kilometers long subscriber line ver is equivalent, so that all telephones behave as if they had been over a relatively long time characterized in that the matching circuit 30 line would be connected. This measure is at least one winding of the over- not only costly, but also has the disadvantage of that in all cases where the distance between the office and the telephone set is not considered to be short can be viewed, either during installation or later on at the participant's premises is to turn off the replica line from the telephone set. The replica management can also not the task of a really good impedance matching between the telephone set and release the line. From the German Auslegeschrift 12 16942 is also already a circuit arrangement for a telephone set with a corrective network to reduce what can be perceived as echoes g g t 2. Circuit arrangement according to claim I, characterized in that the matching circuit is a parallel circuit of a Widerd [R) i Kd weter capacitor (C ₁₁ ) is connected in series, contains and is connected to the line terminals («, b) (Fig. 5).
3. Circuit arrangement according to claim I, there-