DE2936722A1 - METHOD AND DEVICE FOR DETERMINING CHARACTERISTIC VALUES OF A TELEPHONE LINE - Google Patents

Description

In operating a telephone system, it is often necessary to check the condition of a telephone line, particularly the state of the subscriber loops that connect telephone lines to a central office. So far, these measurements have been carried out using various sets of testing equipment or devices have been connected to the line in succession to separately determine each of the parameters sought. A detailed analysis involves measuring at least thirteen separate parameters, including any stray AC voltages, DC voltages, leakage resistances and line capacitances between the tip connection and ground, ring connection and ground as well as between tip and ring connection of the subscriber loop as well the frequency of the stray AC voltages. It is evident that the separate determination of each of these parameters determining the state of the subscriber loop is a lengthy and arduous undertaking.

US Pat. No. 4,028,507 describes an improved device for measuring the various parameters, where the tip and ring connection are acted upon with different * potential series in relation to ground and thereby the resulting currents must be measured. The various parameters can be calculated from these measurement results will. In this described arrangement, different series of direct and alternating voltages must be used

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to measure the respective leakage resistances and the (primarily capacitive) line reactances. Additionally Filters are necessary to remove stray AC voltage signals that occur in the line during AC voltage measurements keep away.

The invention is based on the knowledge that by applying or connecting only three successive DC voltage states to or with the line via known tip connection and ring connection resistors (instead of direct application the voltages on the line) and recording the resulting transient (or transient) charges and of the equilibrium current through these resistances, sufficient information is obtained for the thirteen listed, to derive different parameters of the subscriber loop and that thereby the separate application with AC voltage signals for the reactance studies can be omitted. In a typical implementation This measurement takes less than 3 seconds, most of which is required is to let the line come into the equilibrium state (so that the transient or transient charge is measured can be changed) if the voltage state of the line is changed. In this way the measurement time is right on related to the leakage resistances and the capacitances of the loop.

According to the invention is a measuring or testing device for measuring a telephone line with tip connection and ring connection lines (for the plug connection) created, having means for separately measuring during a first state of stray currents emanating from the tip port flow through a first reference resistor to ground and from the ring connection via a second reference resistor flow in bulk. The measuring device contains means for measuring the transient (or transient) charge

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and the equilibrium current during a second state flowing through the first and second resistors, if these are in series with first DC voltage sources between the tip connection line and ground or ring connection and ground are connected. The measuring device contains means for measuring the transient (transient) charge and of the equilibrium current flowing through the first and the second resistor when these are in series with the second DC voltage sources between the tip connection and ground or ring connection and ground during a third state are connected, the second voltage sources being different from the first voltage sources Have tension.

In a particularly advantageous embodiment, both sides of the loop are via the reference resistors for measurement the stray currents are grounded, a low DC voltage is applied to both sides of the loop across the resistors during of the second state is applied and in the third state the low voltage is removed from one side. Any state gives two values: a transient (transient) charge flow as a result of the change of state and an equilibrium current flow after the transition (settling). The current values result in any stray voltages that may be present and leakage resistances, while the transient (transient) charges give the capacitance values.

The invention also encompasses a method for measuring the parameters, the individual parameters being determined by the respective, of stray currents flowing through the reference resistors connected to ground on each side of the line are measured and recorded are then individually measured and recorded the transient (transient) charges and the equilibrium currents by the respective ones, in series with the first direct current sources from both sides of the line reference resistors connected to ground flow and

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then individually the transient (transient) charge and equilibrium currents measured and recorded by the respective ones in series with the second voltage sources between each side of the line and ground Reference resistances flow, the second sources having a different voltage ratio than the first and then the various parameters can be calculated directly from the recorded measured values.

An exemplary embodiment of the invention is explained in more detail below with reference to the drawing; in the drawing shows:

Fig. 1 is a schematic block diagram of a

measuring device connected to a telephone line for measuring the telephone line,

Fig. 2 typical, based on the reference resistors

Current waveforms evolving during the three voltage states in the absence of any
Alternating scatter signals,

Fig. 3 shows typical equilibrium current conditions

the tip or ring feeder if there are exchangeable stray parts and the exchangeable component of the current after rectification, and

Fig. 4 shows the transition ^ (transient) current flow at

Stepped direct voltage applied to one side of the line if alternating stray components available.

The block diagram in Fig. 1 shows one with the tip lead t and the ring lead r as well as with the associated Ground g of a telephone line 10 to a telephone device 11

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connected test or measuring device. When the speaking part is in place, the telephone set corresponds approximately to a capacitor C of 0.45 .uF for the line 1O; this capacitance is formed primarily by a DC isolating capacitor in series with a ringer (not shown) in telephone set 11. The leakage resistance R. and the line capacitance C, in series with stray alternation or. DC voltages Vac. and Vdc from the tip connection t to the base connection g and the leakage resistance R and the line capacitance C in series with the stray AC or DC voltages Vac and Vdc from the ring connection r to ground g and the leakage resistance R. and the line capacitance C 'between the tip connection t and ring connection r of the line 10. Since the capacitor C is parallel to the capacitance C, the total capacitance of the tip connection to the ring connection C. = C + C '. The series resistors R. and R of the line 10 are shown as discrete resistors. Normally, these resistance values are small (<3000 ohms) compared to leakage resistances ( » 50000 ohms) of the line 10 and consequently have only a minor effect on the resistance measurements. The line resistances also do not influence the accuracy of the capacitance measurements, since these calculations are based on the total charge flow and not the charge flow for an initial period of time, ie since the basic measurements are only carried out after the transient (transient) voltages have decayed.

In the following description of the measuring or testing device, corresponding elements and wave trains ¹ (for current or voltage), each relating to the tip lead t or to the ring lead r, are denoted by the same reference number or the same symbol, followed by the relevant index t or r. If it is not necessary to differentiate between the allocation to the tip or ring lead, only the reference symbol or symbol is used

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cited. The places in Fig. 1 at which the in Fig. 2, 3 and 4 occur are indicated by corresponding reference numerals. Additionally are all switches (shown only for illustration) at the same time with the same contact reference numbers Contacts connected and this is done under the control of a timing control circuit, which is later is explained in detail.

The two leads t and r of the line 10 are connected by input reference resistors Ri. And Ri (the respective typically in the order of 100 kOhm), connected to switches 13, which have the three different ones affect the line 10 applied voltage states or result. During the three measuring stages, the currents and the transient (transient) charge flows through the Reference resistances Ri, and Ri obtained indirectly by monitoring the voltage drop across them. The adjustment of the test device results from the following description of the function and operation of the device.

During the initial state, both the resistance Ri. and Ri are connected to ground g in order to measure any stray AC or DC voltages Vac or Vdc in line 10 to enable. If the switches are in position 1, stray alternating voltages, which develop via the resistors Ri. or Ri, through capacitors 14, AC / DC converters 15 and switches 16 applied to the respective voltage / frequency converter 17. The use of this converter 17 allows the use of simple Counting method for integration in order to carry out the capacitance measurements. As explained below, the DC voltage measurements (through the stray DC voltages Vdc. and Vdc, leakage resistances and capacitances can be obtained) carried out with directly with the line 10

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connected voltage / frequency converters 17. The AC voltage measurements (which give the stray alternating voltages Vac. and Vac) are carried out in such a way that the transducers 17 about the DC-blocked AC / DC converters 15 are coupled to the line 10.

The output signals of the capacitors 14 are sent to positive zero crossing detectors 20 created. If there is a detectable stray AC voltage component in the line 10 is, the measuring length * will be the time between two positive zero crossings of the alternating voltage component. All DC voltage measurements are synchronized with integer multiples of the cycles of the stray AC component, so that interference from the alternating component is avoided.

The following simplified assumptions are made about the stray AC voltage sources met:

(1) Any stray AC voltage is periodic. If this assumption does not hold, for example if the AC voltage is broadband white noise, the meter is still attempting an ac voltage mean reading However, no other measurement can be carried out because the measuring length cannot be synchronized.

(2) Stray AC voltages at the tip and ring come from a single source. Different sources for Tip and ring with similar or the same amplitudes, but different frequencies result in one similar result as just described.

According to assumption (2), the loop 10 can be reduced to one of the following two equivalents for the alternation measurement: Either the alternating scatter sources for tip and ring are in phase or they are out of phase. This makes phase 0 detects that the output signals of the positive zero crossing

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Detectors 20 are compared in a phase detector 21. The peak-to-ring tensions can be calculated in the following ways be calculated:

Vac _tr = - ^ Vac _tg + Vac _rg - 2. ^^

The output signals of the voltage / frequency converter 17 are applied to counter 22, which results in an output signal Frequency counting η over a preselected length of time results, as will be explained below. In addition, there is an internal 1 MHz clock generator 2 3 is provided, which gives a reference frequency output signal f, which is sent to another counter 24 is created. The counter 24 gives two output signals: (1) a measurement of the measurement time length ^, i.e. the time between successive zero crossings of the scattering alternating component Vac, which are detected by one of the two positive zero crossing detectors 20 are detected; this indirectly affects the resetting of the counter 24,

or (2), if there is no alternating component, the maximum measuring time length T, which always results when the counter 24 is full. Έ * is chosen to be larger

Max

is as the cycle time (period) of the leakage voltage AC signal with the lowest frequency like that

is expected. A typical value is ^ = 100 ms.

Max

Either the measuring length pulses t, TT or the value t

u r max

are fed via a switch 30 and / or an OR gate 25 to a computer stage 26, which also controls the counters and receives the phase output signals η., η and 0 as shown in Fig. 1 to perform the various calculations that are given in Tables I and ΓΙ.

The switch 30 is in the initial state with the output terminal of the detector 20t. However, if there is no stray AC voltage signal is detected, this information is sent to the

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Computer stage 26 passed, which (shown in dashed lines) the connection of the switch 30 to the output terminal of the detector 20 produces. This allows a stray signal to occur at either the tip port and / or the ring port cause the counters 22 and 24 to be reset.

In addition, the computer stage 26 gives reset signals for the counters 22 and 2 4 every time through the OR gate 25 a control signal is emitted. The computer level 2 6 gives the calculated values to a recording and Display unit 27 and also generates control signals for the various switches. If the measurement is in the switch position 1 has ended, the switches 13 and 16 are switched to the respective position 2 by the computer stage 26, to measure stray DC voltages. The switches 13 and 16 are then switched to their respective position 3. In this position, an internal voltage source V (typically V = 50 V) is supplied via the resistors

S S

Ri. And Ri are applied to both t and r and another series of DC voltage measurements is made and the size of the transition charges flowing through the 1 is detected.

and it becomes the size of the resistances Ri. and Ri

When a state of equilibrium is reached (determined by the equality of two successive measurements) the ring connection r is again connected to ground via the resistor Ri, as indicated by switch position 4, and a further series of direct current and charge flow measurements are carried out. It should be noted that the resistance Ri _r can not necessarily be connected to ground, but also to a voltage source of a different size. It is only important that the ratio of the two voltages applied to the resistors Ri. And Ri differs in the switch positions 3 and 4.

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After these measuring processes have been completed, sufficient information is available in the computer stage 26 to enable the measurements to be derived according to Tables I and II and finally the thirteen parameters to be calculated. There are only three of them different voltage states have been applied to the resistors Ri, and Ri. In positions 1 and 2 are Both resistors are connected to ground, in position 3 both resistors are connected to V and in position 4 RL is grounded again, while Ri is still connected to the voltage source V.

The instantaneous output frequency or output frequency f of the voltage / frequency converter 17 is proportional to the instantaneous current i which flows through the resistors Ri. The transfer function of the converter 17 is therefore: f = ki + f_, where k is a gain or proportional _{value and f Q represents} the output frequency of the converter 17 at i = 0. If t is a measure of time and η is a count of the cycles of f, the instantaneous frequency f is given by f = dn / dt. Current i and charge flow q result from the following relationships:

i = 1 / k (dn / dt - f _Q ) and

= / idt = 1 / k ^ ~ / dn - f ₀ Jdt_7.

The charge flow is given for a limited measuring time t by t

q = / idt = 1 / k (N - f _Q V). ο

The mean value T of the current is given by

T = 1 / t * / idt = 1 / k (N / t - f ₀ ).

tr

Here, N = J dn, ie the counting content that has accumulated during the time length t.

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The frequency f of the stray AC voltage is then obtained

to f = 1 / τ.

Typical charge flows and equilibrium currents through the reference resistors Ri. And Ri during the different measuring intervals are shown in FIG. If there is no such voltage, the currents are i. ., and i ₁ as zero during the initial interval when the switches are in position 1 and 2. The transition charge flows Q. and Q during states 2 and 3 result from the voltage changes that are made on both sides of the line 10. This also results in different equilibrium currents i. and i during states 2 and 3.

An alternating component resulting from the presence of a stray alternating voltage originates on the line 10, an equilibrium current i is superimposed according to FIG. The charge flow q during one cycle of the scatter signal is also shown in FIG. This is in the lower part of FIG corresponding current output signal from the AC / DC converter 15 is shown.

Fig. 4 shows the transient (transient) charge that occurs after a change from state p-1 to state ρ (e.g. from State 2 to State 3) flows. The transitional state or transient state is then considered to have expired, if successive measurements show no detectable change in current, i.e. if i _, = i.

The transition charge flow is then as follows:

m-2 _

Zq- V ₁ · ψ

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This is not necessarily the total charge of each Capacity, however, is related to this. This means that the capacitance values can be determined directly from the measurements by making corrections to the leakage resistances as indicated in Tables I and II is. It should be pointed out that a change of state with the length of time C by the computer stage 26 is synchronized. The leakage resistance values are derived from the stable ones that are no longer influenced by the settling Current values i are calculated, which can be easily derived from the given formulas.

Initially, the derived measurement results from the computer stage 26 during the respective switch positions supplied information determined. These measurement results can then be used to perform the intermediate calculations shown and then calculate the required thirteen parameters. These will eventually become the recording and display unit 27 passed on.

This results in a method for deriving thirteen specific parameters of a telephone line from electricity and charge flow measurements of each side of the conduit, where the measured values are taken during only three successive voltage states on both sides of the telephone line can be applied via tip connection and ring connection resistors. This enables the calculation of any stray alternating voltages, - DC voltages, leakage resistances and line capacitances between tip connection and ground, Ring connection and ground and tip connection and ring connection are just as possible as the determination of the stray AC voltage frequencies.

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Panel I.

Switch position

derived {interim calculations of measurement results

ac ti

ac rl

calculated parameters

^Vac tg ^{= T} ac

Vac = i, Ri rg ac rl r

Vac. = 7Vad + Vac ² -2-Vac. -Vac -Cos0 tr ν tg rg tg rg,

f _s = I / t

■ ti

^Vdc tg ⁼ - V ^Ri t ^Vdc rg ⁼ "V ^R V

I. Vi V V2 Vi Vdc _tr = Vdc Vr tg - ^Vdc r _g I.
3 ^T t2 Vg ₂
^V tr2 "V I _t2 -Ri _t ρ - v • V ^V tr2 • * tg * -Vg ₂ ^R tg ^{t93 V} tr3 ^V s ^: r2 ^- . ^V tr2 (known) ¹ U- D - " ^t3V tr3 'r3 ⁼ 'ti rq ν ^V tr2 ^v tg3- ^T r3 " 'rl ^V tg3 ^r S ^{3 V} tr3 Vs
X Vg ₃ = ■ t3- ^R1 t -'r3 Vr ₃ ' = 0-1 r3 ^Ri r ^{r3 V} tr3 4th - V
^v tg3 " ^V rg3 ρ - ^R tr - ^V tg2 V ^ + ¹ P ₂ ^
Vg3

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ORIGINAL INSPECTED

85 to

• Η

Plate II

31

Interim invoices

Q

t2

ORIGINAL "r2 0300 ' ^G tg ' ^{1 / R} tg cn
^^ INSPEC ^{4 Q} t3 ^G rg ' ^{1 / R} rg ο m
ο "r3 ^G tr ■ ^{1 / R} tr CO

■ ^{1 / V} s ^G i '

'tr

/ q Calculated parameters

" ^Q t2 ^tG i ⁺

V ^G rg ⁺

VV ^Q t3 < ^G i ⁺ V

N)

CO ι CO

N) N)

Read 11 e

Claims (4)

Claims Measuring device for a telephone line with the plug tip connection and the plug ring connection leading wires for the direct calculation of the leakage resistance, the line capacities and the stray voltages between tip connection and ground, ring connection and ground, as well as tip and ring connection from measurements, with a device for applying three successive DC voltage states between Tip connection and ground or ring connection and ground, with the two applied voltages in one state of the two applied voltages in the second and third state differ at least in size or ratio 030015/0731 MANlTZ FINSTERWALD HEYN MORGAN 8000 MUNICH 22 ROBERT-KOCH-STRASSE1 TEL. (089) 22 4211 TELEX 05-29672 PATMF ORIGINAL INSPECTED different, and means for separately measuring the tip and ring leads flowing in ^e ürei state equilibrium currents, characterized in that each of the three consecutive states of stress between the tip terminal and ground and ring terminal and ground via first and second reference resistors is applied, and in that Means are provided for separately measuring the junction charges flowing through the first and second resistors to the tip lead and ring lead, respectively. 2. Measuring device according to claim 1, characterized in that a device for the separate Measurement of stray currents is provided, passing from the tip terminal to ground through the first reference resistor and from the ring connection to the ground through the second reference resistor that means for applying the first and second DC voltages across the first and second resistors between the tip connection and ground or Ring connection and ground and then for separate measurement of the transition charge and the equilibrium current are provided by the resistors and that devices for applying third and fourth DC voltages, with a ratio different from the first and second voltages, across the first and second Resistances between tip connection and ground or ring connection and ground and then for separate measurement the transition charge and the equilibrium current are provided through the resistors. 3. Measuring device according to claim 2, characterized in that three of the four direct voltages are of the same order of magnitude. 030015/0731 4. Measuring device according to claim 2, characterized in that further means for measuring any alternating components in the stray currents are provided that devices for detecting the zero crossings the alternating components are provided in the stray currents and that devices are provided that detect if there is no noticeable change in the current value of successive zero crossings, to make the measurement to end the transient charge and to initiate the measurement of the equilibrium current. 030015/0731