CN2783650Y - Telephone line tester - Google Patents

Abstract

The utility model relates to a detecting device for a telephone line of a user in a telephone network, which is composed of a constant current source, a voltage comparator A, a voltage comparator B, a receiving voltage comparator A, a processing unit of voltage comparator signals and a timing clock source for supplying a working timing clock of a processing unit and timing. The components are respectively connected with a change-over contact switch of a telephone line to form into the device. After the utility model is coupled in the telephone line, collected data are analyzed and processed and provide the correct and effective judgement for the line breakage or the terminal connection telephone on the basis of the constant current source and characteristic differences for the charge and discharge of the telephone and the charge and discharge of the line. The detecting device for the telephone line has the advantages of good practicality, precision and good effect on the detection of the telephone line of the user.

Description

A kind of telephone line testing apparatus

Technical field

The utility model relates to a kind of device of in telephone network user telephone line being tested, and belongs to communication technical field.

Background technology

Fixed-line telephone network telephone line to the user side of relying provides communication service to the user.In having hundreds of millions of users' telephone network, for making each subscriber phone unimpeded, primary work is the telephone line that will safeguard sensible every household.The route survey equipment of configuration passes through periodically measurement circuitry parameter in the telephone office, determines whether circuit is good, needn't wait for subscriber complaint, just can in time find fault, fix a breakdown, and improves service quality.The project that line test equipment in the telephone office is measured telephone line has: line-to-line resistance and line resistance to earth, line-to-line electric capacity and line direct-to-ground capacitance, line-to-line direct voltage and line direct voltage over the ground, and line-to-line alternating voltage and line alternating voltage over the ground, totally 12 parameters.According to the result who records, judge that circuit has broken string, short circuit, the defective insulation of denying or bumps other circuit then.In fact, during line test equipment is measured telephone line in telephone office, because the terminal of telephone line is connected to user's telephone set, therefore, in route survey, the parameter that measures also contains the parameter that telephone set presents circuit except the physical parameter of telephone line itself such as resistance, electric capacity, voltage.Wherein, the physical parameter change at random of telephone wire itself is little, and the telephone set network of various standard and model is different, and is also inequality with the interface parameters of telephone network.Especially, the capacitive reactance characteristic that when the telephone set on-hook, presents, the capacitance that has is very little, almost with circuit in line capacitance suitable, therefore, how to differentiate telephone line broken string, do not connect and still connected telephone set, and the test under the long transmission line condition, be a difficult problem of failing to be solved in the present telephone line test.Must give the requirement of correct decision at telephone office's line upkeep work, the utility model provides a kind of novel telephone line testing apparatus by development.

Summary of the invention

The purpose of this utility model is, by telephone set under the constant-current source being discharged and recharged and the variance analysis of circuit charge-discharge characteristic, and need accurately to judge whether to break or the requirement of terminating phone in the telephone line measurement, provide a kind of and can judge correctly, effectively that telephone line has trouble-free measurement mechanism.

The utility model telephone line testing apparatus constitutes by inserting telephone wire terminal, switch, constant-current source, voltage comparator A, voltage comparator B, processing unit and clock source.The telephone line testing apparatus inserts telephone line, in to route survey, because there is line capacitance in the line-to-line of telephone line, and on the telephone wire the machine of answering the call presents circuit when off-hook not also is capacitive reactances, therefore, being difficult to the distinguishing terminal telephone set in general route survey, to be in hook state still be that line disconnection has malfunction.Analyze in the telephone line phone circuit characteristic and line characteristic as can be known, the general every kilometer loop resistance of telephone line about 200 ohm with the about 47nF of electric capacity total value (nano farad).During the ordinary telephone set on-hook, it on the circuit is the ringing circuit that one group of resistance, electric capacity are connected with rectifier bridge that telephone set is connected on, and electric capacity is generally 1 μ F (microfarad), resistance be 1k Ω～2k Ω (kilohm).The ringing circuit of little electric capacity telephone set can equivalence be a resistance and the connecting of electric capacity, and electric capacity is generally 0.22 μ F (microfarad), the nearly 10k Ω of resistance (kilohm), as god's board HW200P/T cordless telephone.Because telephone line is different in size, the line capacitance amount is also different thereupon.When circuit was long slightly, the line capacitance amount was suitable with the phone capacitance, and therefore, capacitance between simple slotted line judges that whether circuit breaks or connect telephone set, tends to judge by accident.The utility model telephone line testing apparatus discharges and recharges the data that collect with circuit charge-discharge characteristic difference according to phone under constant-current source, carries out analyzing and processing, and correct judgement is provided.Judge that principle is as follows:

Adopt the constant current source charging method to measure the capacitance of telephone line, and when line conditions judged, setting voltage monitoring point V1, V2 (V2＞V1).In the test, earlier circuit is discharged, then to line charging, along with voltage rises, recording voltage is charged to the required time T of V1, V2 1, T2.Wherein, suppose that the constant-current source electric current is I, in the electric capacity charging process, voltage, electric capacity and time relation have the following differential equation:

$I=C\frac{\mathrm{dv}}{\mathrm{dt}}---\left(1\right)$

During charging,, obtain formula if circuit initial voltage V0 separates the differential equation (1):

$V=\frac{I}{C}T+V0---\left(2\right)$

Then have with respect to V1 and V2:

$V1=\frac{I}{C}T1+V0---\left(3\right)$

$V2=\frac{\mathrm{<figure-callout\; id="2"\; label="I\; C\; T"\; filenames="Y20042009111900081.png"\; state="\{\{state\}\}">I</figure-callout>}}{C}T2+V0---\left(4\right)$

Formula (3) is divided by with formula (4), obtains formula (5):

$\frac{V2}{V1}=\frac{I\&times;\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="Y20042009111900081.png"\; state="\{\{state\}\}">T</figure-callout>}2+C\&times;V0}{I\&times;T1+C\&times;V0}---\left(5\right)$

According to formula (5), under the circuit different conditions, can obtain respectively:

1) in broken string (or the machine of not answering the call) circuit, line capacitance should be discharged fully, and V0=0 can obtain in the charging process thus:

$\frac{V2}{V1}=\frac{I\&times;T2}{I\&times;T1}=\frac{T2}{T1}$

2) in the equivalent electric circuit that connects the plain old telephone machine circuit, because the voltage discharge off loop on the capacitor C 2 has residual voltage to exist on the electric capacity, and the size of voltage is generally the C1/C2 of feed voltage, and again because V0＞0, T2＞T1 according to formula (5), can obtain:

$\frac{V2}{V1}=\frac{I\&times;\mathrm{<figure-callout\; id="2"\; label="T"\; filenames="Y20042009111900081.png"\; state="\{\{state\}\}">T</figure-callout>}2+C\&times;V0}{I\&times;T1+C\&times;V0}<\frac{I\&times;T2}{I\&times;T1}=\frac{T2}{T1}$

3) in connecing the circuit equivalent electric circuit of little electric capacity telephone set, because resistance R is bigger, higher initial voltage V0 is arranged during charging, and V0=IR＞0, again because of T2＞T1, can obtain equally:

$\frac{V2}{V1}<\frac{T2}{T1}$

According to above analysis, during the circuit broken string, the ratio of voltage equates with the ratio of time; And concerning the circuit that is connected to telephone set, equivalent capacitor equivalent is in parallel in circuit selfcapacity and phone electric capacity on the circuit, under both actings in conjunction, the ratio of voltage is less than the ratio of time, general little more than 10%, thus, can judge correctly that circuit is broken string or has connect telephone set.

The advantage of the utility model telephone line testing apparatus is, discharges and recharges the data that collect with circuit charge-discharge characteristic difference according to telephone set under the constant-current source, carries out analyzing and processing, and correct judgement is provided.Thereby overcome simple measurement phone line capacitance, judged whether circuit breaks or answer the call machine, the disadvantage that can judge by accident has also solved the difficult problem in the telephone line test.

Description of drawings

Fig. 1 is the utility model telephone line testing apparatus structural representation.Wherein, 1-inserts telephone wire terminal, 2-switch, 3-constant-current source, 4-voltage comparator A, 5-voltage comparator B, 6-clock source, 7-processing unit.

Fig. 2 is the equivalent circuit diagram of the utility model telephone line testing apparatus test telephone circuit.

Fig. 3 is the telephone line equivalent circuit diagram during the ordinary telephone set on-hook in the utility model telephone line testing apparatus test telephone circuit.

Telephone line equivalent circuit diagram when Fig. 4 is the on-hook of the medium and small electric capacity telephone set of the utility model telephone line testing apparatus test telephone circuit.

Embodiment

Be described in detail the embodiment that meets the present utility model theme below in conjunction with accompanying drawing.

Embodiment

By inserting telephone wire terminal 1, switch 2, constant-current source 3, A voltage comparator 4, B voltage comparator 5, clock source 6, processing unit 7, press electrical schematic diagram and connect, constitute the utility model telephone line testing apparatus.Testing apparatus inserts telephone line, and in to route survey, the effect of each several part is as follows:

1) switch 2 is equivalent to a changeover contact, and when switch contact point a-b connection, when contact point c was disconnected, testing apparatus discharged to test line; When contact point a-c connection, when contact point b was disconnected, testing apparatus was tested tested telephone line;

2) when switch contact point a-c was communicated with, constant-current source 3 charged to tested telephone line with milliampere level electric current;

3) reference voltage of A voltage comparator 4 is set to V1.When constant-current source 3 between tested telephone line charge period, when make and break contact c went up voltage and reaches V1, A voltage comparator 4 had signal output immediately, sends to processing unit 7;

4) reference voltage of B voltage comparator 5 is set to V2 (V2 is greater than V1).When constant-current source 3 between tested telephone line charge period, when switch 2 contact c went up voltage and reach V2, B voltage comparator 5 is output signal immediately, sends to processing unit 7;

5) clock source 6 produces megahertz MHz level periodic signal, sends to processing unit 7, processing unit 7 work clocks to be provided and to carry out timing;

6) processing unit 7 receives the signal that A voltage comparator 4 sends, and writes down its time T1; Receive the signal that B voltage comparator 5 sends, write down its time T2, according to the relation of the ratio of the ratio of T1, T2 and V1, V2, judge whether circuit connects phone or broken string then.

The job step of processing unit and result judge as follows:

A, processing unit notice switch are communicated with contact a-b, and break c is to line discharge;

B, processing unit notice switch are communicated with contact a-c, and break b to line charging, and begins to start timing;

C, processing unit receive the signal that A voltage comparator 4 is sent here, and the time T 1 of signal received in record;

D, processing unit receive the signal that B voltage comparator 5 is sent here, and the time T 2 of signal received in record;

E, processing unit calculate according to reference voltage V1, V2 value and T1, T2 value to inserting voltage comparator in advance, if:

V2/V1＜T2/T1 then circuit is normal, and user terminal has connect telephone set;

V2/V1 ≈ T2/T1 is the circuit broken string then.

The utility model telephone line testing apparatus discharges and recharges data with circuit charge-discharge characteristic difference by being captured in phone under the constant-current source, carries out analyzing and processing, thereby right judgement is provided, and has solved the difficult problem in the telephone line test.

Claims (2)

1, a kind of telephone line testing apparatus, comprise the telephone line incoming end, the changeover contact switch, constant-current source, voltage comparator A, voltage comparator B, processing unit, the clock source, it is characterized in that, device connects the constant-current source that charges to tested telephone line respectively by the changeover contact switch that connects telephone line, send a signal to the voltage comparator A of processing unit, send a signal to the voltage comparator B and the received signal of processing unit, writing time, judge circuit good or the processing unit of broken string and the clock source formation that processing unit work clock and timing are provided.

2, telephone line testing apparatus according to claim 1 is characterized in that, in the telephone line testing apparatus, may command changeover contact switch is communicated with contact a-b, and break c is to line discharge; The control transformation contact switch is communicated with contact a-c, break b, and to line charging, the processing unit that begins to start timing can receive the time T 1 that signal received in signal that voltage comparator A sends here and record; The time T 2 of signal received in signal and record that the reception voltage comparator B is sent here, and by voltage comparator reference voltage V1, V2 value and the time T 1, the T2 value that preset, calculate V2/V1＜T2/T1, and circuit is normal, and user terminal has connect telephone set; V2/V1 ≈ T2/T1, the dateout of circuit broken string.

Images