JPS5952962A - Circuit for detecting polarity inversion of trunk line - Google Patents

Abstract

PURPOSE:To contrive a safety countermeasure to the falling of thunder-bolt and static electricity, by insulating the polarity inverting circuit of a trunk line from the main wire in DC by using a magnetism-sensitive element. CONSTITUTION:When input terminals L1 and L2 of a trunk line are used as the positive and negative sides, respectively, and a telephone set TEL makes a call, a loop current is made to flow through the L1, pickup coil L, TEL, and L2 in the described order and supplied to a magnetism-sensitive element DM composed of a semiconductor Hall element, etc., by electromagnetic induction insulated in DC. By the supply of the loop current, the magnetic resistance value RA of the element DM is reduced and the relation between the RA and a fixed resistance value RB attains to RA<RB. Therefore, the electric potential at an input terminal (a) of an operational amplifier AMP is mode higher than that at another input terminal (b) and the electric potential at a point (p) is also raised, and then, a Zener diode ZD1 conducts and, consequently, a transistor Q1 also conducts. When the direction of the electric current of the trunk line is inverted by the response of a called subscriber, the direction of a magnetic field generated in the above mentioned coil L is reversed and the relation between the RA and RB attains to RA>RB, and, therefore, a Zener diode ZD2 conducts and an inversional output is obtained at the output terminal OUT2 of a transistor Q2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a detection circuit for detecting polarity reversal of a central office line due to a response from a called party.

A call rate calculation device β or an automatic reporting device attached to a telephone device makes a call from the telephone device to the other party, and
It is designed to be activated after the person fails to respond.

For this reason, as means for detecting a called party's response, a polarity inversion signal of the central office line is detected when the called party answers, and the driving section of the device is driven by this detection signal.

Conventional local office line polarity reversal detection circuits include a combination circuit of a relay and a diode as shown in FIG. 1, and one using a photocoupler as shown in FIG.

In Figure 1, LI and L2 are office line input terminals, Dl and D2 are silicon diodes, and R is a relay.
・When the caller receives a call, the local current flows through the relay of -D, -D2, -L2, but due to the polarity reversal of the station line due to the called party's response, the local current changes to L2-D2. Since the flow relay R operates in the loop of -R-L, the meter signal at the contact point (not shown in the drawing) of the relay R can be used as the polarity reversal detection signal of the station line.

Further, in FIG. 2, the same reference numerals as in FIG. 1 indicate corresponding parts, and PC, PC2 are photocouplers. Office line input end,
If L2 is set to the positive side and L2 is set to the negative side, when a call is made from the telephone device, the photocoupler PC, turns on, and when the polarity of the office line is reversed by the called party response VC, the first coupler Pc, turns off, and the photocoupler PC, turns off. Coupler PC2 is turned on. In addition, when the station line input terminal is set to the negative side and L2 to the positive side, the photocoupler PC2 is turned on when a call is made from the word-compounding device, and when the polarity of the station line is reversed by the called party's response, the first coupler PC2 is turned off. 7° on the side
) C is turned on. In this way, this detection circuit detects the state of the central office line at the time of original call from the telephone '1'' EL and the state of the central office line after the called party responds using the photocoupler PC, PO2. At the station line input end, , regardless of whether the initial polarity of L2 is positive or negative, the 7th first converter PC, ,
The polarity reversal of the station line can be detected by the output of the collector of the photol-run/star of PO2. More specifically, even if the initial polarity of the central office line input terminals 1-11 and L2 is changed due to subsequent construction at the telephone office, it is possible to detect the polarity reversal of the central office line. , Here, in order to facilitate understanding of the present invention, Figure 3, Figure 4.
The figure shows a block tire diagram of the outer part of the central line circuit of the above-mentioned apparatus equipped with a central line polarity reversal detection circuit.

In Fig. 6, the quill circuit A D i to the office line is a metallic connection using metal contacts, etc., and the direct current resistance at the office line input end, , L2 is the telephone circuit TC (transmitter resistance + transformer). It is the sum of the equal dynamic resistance of 90Ω of the winding resistance of the central line and the equal dynamic resistance of the polarity reversal detection circuit 8 of the central line.

Recently, J-r.
If a semiconductor connection is used as shown in Fig. 4 instead of the conventional 7-point connection, the equal dynamic resistance of this electronic digital oscillator circuit EDi will be 1 due to 1-run/metal. Voltage drop o6■, current 2 at line resistance 1500Ω
DnLA, so 0.6V10.02A:=30Ω
, and the equal dynamic resistance of the Norinon rectifier circuit RF C is 1.2, and the voltage drop is 1.4.
Since the current is 2 OnA when the V line resistance is 1500Ω, the equal dynamic resistance of the telephone circuit TC (transmitter resistance + transformer winding resistance) is 90Ω, so the gold side of this DC is 190Ω.

In the case of Figure 1, the equal dynamic resistance of the conventional polarity reversal detection circuit of the station line is 0.7 V when the voltage drop across the silicon diode D2 is 0.7 V.
, line resistance 1500Ω current 20rrb A 0.7
v10.02A:=35Ω The DC resistance of the coil of relay R is 5Ω, and the total is 70Ω. Also, as shown in Figure 2, photocouplers PC are connected in parallel in the forward and reverse directions.
The equal dynamic resistance when Pc2 is installed in series with the office line is that the voltage drop due to 2021 photocouplers PC is 1.
Current 20 yrI at 4V line resistance 1500Ω.

Since it is A, 1.4 Vlo and 02Δ=70Ω.

Therefore, in Figure 4, it is necessary to install the conventional office line polarity reversal detection circuit shown in Figure 2 in the circuit with the electronic dial transmitting circuit ED1. "The direct current resistance is 260 ohms, which is 14 times less than the regulation in Japan for direct current resistance of 220 ohms or less."Installing a tocoupler in the station circuit was fraught with the risk of damage from lightning or static electricity.

In order to eliminate this drawback, the present invention provides several DC resistors in the central line.
Connect the coil of No. and the coil in the first row.
Connect the nano 9- to the straight 11, and attach the magnetically sensitive element to the coil 1. By electrically separating it from the station line so that it is sensitive to the magnetic field generated by the station, there will be no damage caused by lightning or static air, and the polarity reversal of the station line when the victim responds will cause the station line to become υ To provide a polarity reversal detection circuit for a central line that has extremely low direct current resistance and is resistant to drops and static electricity, which is characterized by detecting the magnetic field generated in the coil by the magnetic element when the direction of the current changes. .

Next, the present invention will be explained in detail based on the drawings.

51/1 is an embodiment of the present invention; L is a coil with a DC resistance of several ohms; C is an AC bypass circuit; DM is, for example, a DM209SDME magnetic sensitive element manufactured by Sony Corporation; A1. AP is an operational amplifier, and the output dark blue of the magnetically sensitive element is
and I) are respectively operational amplifiers f\IJIPCD11″
Connected to the inverting input and the inverting input, vcc is the voltage of the electric wire E, and ■(, is the resistor to set the potential at the output point PV of the operational amplifier A k4p to VCC/2. ZD, , ZI
) 2 is a zener quart, and the zener direct pressure is the desired pressure and deviation within the range of VCC/2 or less. Q, ,
The same reference numerals as in FIGS. 1 and 2 indicate corresponding parts.

Figure 6 shows the equivalent circuit of the magnetically sensitive element DI in Figure 5, where no magnetic field is applied, RA = RB, and the solid and broken arrows indicate the direction of the current flowing and the direction of the current flowing. The direction of the magnetic field generated by is shown.a and b are the output lines, respectively.

Figure 7 shows the output point P of the operational amplifier A kA P when the output generated in the magnetic element DM is input to the operational amplifier A kA P when a local current flows through the L and a magnetic field is generated. The X-axis direction shows the magnetic flux density, and the Y-axis direction shows the output voltage of the amplifier AMP.

Next, the operation will be explained.

Telephone T E with office line input terminal L1 on the positive side and L2 on the negative side
When the signal is transmitted from L, a current I flows in a loop of -L-place-L2. At this time, due to the magnetic field generated by the filler LK, the magnetic resistance RA of the magnetically sensitive element DM becomes RA<T(B,
When a voltage is generated on the output line a and input to the non-inverting input side of the operational amplifier, the operational amplifier AMP becomes higher than the P black reference voltage.
Voltage output.

The output pattern is shown in FIG. 7f. The output passes through a Zener diode ZD and a transistor. 1 is turned on and output to output terminal OUT1. In addition, it is a transistor. 2 is PN
P) It is a transistor and ZD2 has a Zener voltage of VCC/
2<VZD2 (VCC, so this transistor is off. 2 is off.

Next, when the called party answers, the polarity of the station wire is reversed, causing the local current to go in the opposite direction. At this time, the magnetic field generated in the coil L causes the magnetic resistance RB of the magnetosensitive element DM to become RB<RA, and a voltage is generated in the output line. However, when input to the inverting input side of the operational amplifier AMP, the operational amplifier AMP outputs a voltage lower than the reference voltage at the P point. The output pattern is shown in Fig. 7g.

At this time, the current is electric mE, +- transistor. 2 emitters,
A loop of the Zener diode ZD2 and the operational amplifier AMP turns on the transistor Q2 and outputs the output terminal 0UT2. Note that ZD has a Zener voltage of vcc/2<v
Since zD2 (vcc), the transistor Q1 is off. Also, when the office line input terminal is set to the negative side and L2 is set to the positive $11i, and a call is made from the telephone connection, the transistor Q2 is turned on, and the transistor Q1 is turned off, and the office line is turned off. The polarity reversal turns on transistor Q1 and turns off transistor Q2.

As described above, the polarity reversal detection circuit of the central office line according to the present invention is as follows.

By detecting the difference in the direction of the current flowing through the filter I connected to the office line, the state of the office line when making a call from a telephone installed and the state of the office line after the called party answers is detected. Therefore, it is possible to detect the polarity reversal of the office line regardless of whether the initial polarity of the office line input terminals "I" and "L2" is positive or negative.

A capacitor C provided in parallel with the coil L is a bypass capacitor provided to avoid AC loss.

Furthermore, in one embodiment of the present invention, DM209SDME manufactured by Sony Corporation was used as the magnetically sensitive element; however, magnetically sensitive elements generally include semiconductor Hall elements, semiconductor magnetoresistive elements, ferromagnetic metal magnetoresistive elements, etc. It is easy to see that the device can be used in the present invention.

As explained in detail above, the magnetic field generated by a current flowing through a coil with a DC resistance of several ohms can be detected by a magnetically sensitive element based on the direction in which the current flows. Extremely low compared to (・
Since it is a value current resistor, it can also be used in a device using the electronic dial oscillation circuit shown in FIG. 4, and it is not destroyed by lightning or static electricity, so it has a great practical effect.

[Brief explanation of drawings]

Figures 1 and 2 show conventional examples of polarity reversal detection circuits for station lines. FIGS. 7 and 4 are block diagrams showing the main parts of the station MN circuit of the device having the station line polarity reversal detection circuit. FIG. 5 shows an embodiment of the station line polarity reversal detection circuit according to the present invention. FIG. 6 shows an example of an equivalent circuit of a magnetically sensitive element. FIG. 7 shows the output waveform at the output point P of the operational amplifier shown in FIG. S...Polarity reversal detection circuit, MDj/mountain...Dial circuit TC...Telephone circuit, EDj...
・Electronic Kuiyato - Transmission circuit REC... Bridge rectifier circuit, AMP... Operational amplifier 1) M...
... Magnetism sensitive element, a-b... Output line, L...
・・・Coil C・・・Capacitor patent applicant Nihon Tsushin Kogyo Co., Ltd.

Claims (1)

[Claims] In a circuit that detects polarity reversal of a station line, a coil and a capacitor connected in parallel with the fill are connected in series to the station line, and a magnetically sensitive element is provided so as to be magnetized to the magnetic field generated in the coil. 1. A polarity reversal detection circuit for a station line.