HU193822B - Subscriber's telephone set operating with very long balanced pair - Google Patents

Abstract

The present invention relates to a very long symmetrical pair of subscriber telephone equipment having directional coupling and signaling circuitry, a subscriber transmission and a reception channel formation unit, and a center-side transmission and a reception channel-forming unit. The device according to the invention is that the transmitting subscriber channel formation unit (A) and the transmitting center-side channel-forming unit (B) is a baseband transmission device, a receiving subscriber channel-forming unit (C), and a carrier-centering unit (D) on the receiving center-side. transmission device. (Figs. 1 and 2) Fig. 1 (W-IUWfc J2L «-LL! O d U-UkH 40 1 39 h« pOftt ------- π - ι L 'RÖh> , Ί.22Ώ Take 0.05-0.3kHz Figure 2

Description

BACKGROUND OF THE INVENTION The present invention relates to a very long symmetrical pair subscriber telephone apparatus having directional coupling and signaling circuits, a subscriber transmit and receive channel mapping unit and a center side transmit and receive channel mapping unit.

Such devices are known per se and can also provide quality telephony services to subscribers remote from telephone exchanges.

It is known that the ohmic resistance of the cable and AC damping increase proportionally with length, limiting the allowable distance between the control panel and the subscriber so that the line DC current does not fall below the minimum value specified by the control panel type and the damping does not increase. more than prescribed. Otherwise, the connection will become impossible to build or understandable.

The line current can be increased by increasing the supply voltage. The problem of contact protection can be solved by using an electronic circuit. Such an arrangement is disclosed in U.S. Patent No. 171,334.

A symmetrical negative impedance amplifier can be used to reduce the attenuation and amplify the signals in the bidirectional direction to the same extent.

The disadvantage of this method is that the amount of amplification that can be applied is limited, since in addition to high amplification, small parameter uncertainty can also result in a gain. Depending on the amplifier type, stricter or looser specifications for cable quality and construction must be made.

Significant gain can only be achieved with fencing systems, where a different frequency band is used to transmit the bidirectional signal. A more common example of such equipment is the SEL Extra-Phone (STC Handbook No. S1250 Subscriber Carrier System) using carrier frequencies of 40 and 64 kHz.

The disadvantage of the apparatus is that since the attenuation of the cables is higher and the crosstalk protection at these frequencies is lower than the baseband, the spacing without the repeater amplifier is not greater than that of the baseband.

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the drawbacks of known centered subscriber line telephony devices operating on a known symmetrical pair, providing a device which, without the need for a repeater amplifier, bridges significantly longer distances than known solutions with the qualitative and quantitative characteristics required.

The subscriber telephone apparatus of the present invention is based on the discovery that combining baseband transmission and carrier frequency resolution can provide a subscriber telephone apparatus which, using a separate transmission band in the two transmission directions, allows a higher gain than the above solutions. The lower the frequency of the connection, the greater the distance that can be bridged.

The object is achieved by the apparatus described in the introduction, the transmitting subscriber channel forming unit and the transmitting center side channel forming unit providing baseband transmission, the receiving subscriber channel forming unit and the receiving center channel forming unit transmitting frequency transmission device.

In another embodiment of the apparatus according to the invention, a dynamic compressor is provided at the input of the transmitting subscriber channel generator and the transceiver center channel generating unit, and a dynamic expander at the output of the transmitting center channel channel generating unit and the receiving subscriber channel generator.

According to a further embodiment of the invention, a subscriber power supply unit is connected to the line on the subscriber side.

In a further embodiment, a control signal generating circuit is coupled to the controlled amplifier of the transmitting subscriber channel generator with its logarithmic output, the linear amplifier output of the control amplifier of the receiving subscriber channel generator and its input to its comparator circuit.

In a further embodiment of the apparatus according to the invention, the transmitting center-side channel mapping unit comprises a low-frequency constant transmission and a high-frequency control amplifier that maintains the signaling frequency amplitude at a constant level.

In a further embodiment, the isolation amplifier in the control amplifier is connected to RC circuits, the low pass branch is connected to a constant gain amplifier, and the high pass branch is controlled by an amplifier amplifier, and their output is fed to a sumer.

According to a further embodiment of the invention, the subscriber data input is connected via a data modulator and a bandpass filter to the transmit channel mapping unit adder, through a center-side data input data modulator and a bandpass filter to the receiver center channel mapping unit demultiplexer is connected to a subscriber data output, the control center channel generator amplifier of the transmitting center is coupled to a center data output via a bandpass filter and a data demodulator.

In a further embodiment, in the control panel unit, instead of the hybrid transformer and the connecting signal wire, the stage is symmetrical to the dynamic expander,

-2193822 has an asymmetric stage integrated into the dynamic compressor and the signal wires are directly connected to the terminals of the quad-wire center.

The invention will now be described in more detail with reference to the drawings. The attached drawings show

Fig. 1 is a view showing the subscriber transmitting and receiving channel forming units of the apparatus according to the invention;

Fig. 2 is a block diagram of the center transmit and receive channel forming units of the equipment,

Fig. 3 is a frequency attenuation diagram of a symmetric subscriber pair, a

FIG. 4 is a variant of the subscriber unit control signal generating circuit, FIG

FIG. 5 is an embodiment of a control amplifier control channel-side channel generator, a

Figure 6 is a block diagram of a method of connecting to a 4-wire center.

The subscriber telephone apparatus of the present invention comprises a subscriber and exchange unit, between which a symmetrical pair of subscribers establish transmission, the subscriber device or subscriber unit. and a pair of terminals that connect to the control panel, providing a simple cable-equivalent operation with quality characteristics that are much shorter than the actual one.

The subscriber unit of the apparatus, as shown in Fig. 1, is connected to the subscriber by means of directional coupler and signaling circuits to the subscriber, and towards the symmetrical pair by means of the subscriber CS '. Between the two is located A transmitting subscriber channel forming unit and C receiving receiving channel subscriber channel forming unit. The subscriber side directional coupler and signaling circuits of the HE are connected to the subscriber unit by a hybrid transformer H 'having a ring generator 1, a power supply source 2 and a loop current monitoring circuit 2 connected in series to its subscriber side. Downstream of the hybrid transformer H ', some elements of the transmitting subscriber channel mapping unit A, such as a dynamic compressor 3, a sound bandpass filter 4, and then an adder 5, are output, the output of which is signaled via the downstream filter CS'. then on the line. The adder 5 is connected to a further input by a signal frequency generator 8 above a speech band and a data signal source via a data modulator 9 and a band filter 10. The signaling frequency generator 8 is also coupled to the loop current monitor 2. In the subscriber power supply unit T connected to the symmetrical pair, the converter 11 is connected to the power supply input of the subscriber unit and the electronic circuits. The receive subscriber channel mapping unit C is connected to the line directional coupler CS 'with a carrier frequency band filter 12 with a carrier frequency filter 12. This is followed by the control amplifier 13 by the demodulator 14 including a bandpass filter 15 and a limiter 16. Demodulator 14 has a frequency filter 17 coupled to hybrid transformer H 'via dynamic expander 18. From the demodulator 14, a data demodulator 20 drives the data output by applying a bandpass filter 19. The demodulator 14 is even connected to a comparator circuit 21 after forming a single component. The comparator circuit 21 is connected to the control signal generating circuit 22 and the bell generator 1 on the one hand.

As shown in Figure 2, the unit's center-side unit is connected to the center by HK center-side directional coupler and signaling circuits, and the symmetric pair pair CSC center-side directional coupler. Between the two is located the transmitting center B channel forming unit and the receiving center D channel forming unit. At the CS 's side-sided directional coupler, the center panel and earth are connected to the symmetrical pair of wires. A low-pass filter 23, a control amplifier 24, are connected in series to the CS center side-directional coupler in the B-directional channel-forming unit B. From the latter output, there are 25 audio bandpass filters and 26 dynamic expander leads to the hybrid transformer H ', and 31 band filters and 32 data demodulators are connected to the data output. In addition, a bandpass filter 27, a rectifier 18 and a difference detector 29 are provided between the output of the control amplifier 24 and the control input. The rectifier 28 is also connected to the signal conductor of the directional coupler and signaling circuits on the HK control panel. From the ring signal dilator 33, the ring signaling β line is connected to the signal line or connected to the carrier frequency generator 30 in the channel-forming unit D of the receiving center D. In this unit, the hybrid transformer H is connected by a dynamic compressor 34, a sound bandpass filter 35, an add-on circuit 36, a modulator 37 and a bandpass filter 38 by serially connecting a CS center side directional coupler. A data modulator 39 and a data input 40 are passed to the adder circuit 36 via a data modulator 40. A fencing frequency generator 30 is also connected to the modulator 37.

In the subscriber unit, the signaling frequency generator 8 operates when the loop current monitor 2 signals direct current in the subscriber unit circuit. Direct current from the line is provided by powering the electronic circuits and the subscriber unit by intervening a DC converter 11 preferably including a buffer battery. From the line, the subscriber CS 'is sideways3

The signal coming through the -3193822 interface is applied to 12 fencing band filters, 13 control amplifiers, and 14 demodulators. The demodulator 14 is preferably a multiplier type switching signal produced by a bandpass filter 15 and a limiter 16 connected to the controller amplifier 13. From the output of the demodulator 14, the speech signal is transmitted to the receiving side of the hybrid transformer H 'by means of an audio filter 17 and a dynamic expander 18. The data signals transmitted during the speech band can be recovered by interleaving the band filter 19 and the data demodulator 20. The equivalent of the signal from the demodulator 14 is applied to a comparator circuit 21, the output of which controls the control signal generating circuit 22 and the ring generator 1. The latter operates when a carrier frequency signal is received from the line and DC is not flowing through the subscriber unit. On the center-side unit side of the center-side unit CS ', the direct-current generated by the central unit feeds the subscriber unit and charges its buffer battery. A low-pass filter 23 and a control amplifier 24 are connected to the CS center side directional coupler. From the latter output, the speech signal passes through the HF transformer 25 to the hybrid transformer H and transmits to the control panel. closing the line DC to the center and activating a carrier frequency generator 30 for receiving the uplink. From the output of the controller amplifier 24, it is selected by the bandpass filter 31 and the data demodulator 32 outputs the data signal transmitted over the speech band. The carrier frequency generator also starts when the ring signal detector 33 indicates the presence of a ring signal. The signal from the control panel is received from the hybrid transformer H 'to a dynamic compressor 34, a sound bandpass filter 35, an adder circuit 36 and then a modulator 37, the output of which is transmitted to the central side directional coupler CS via a bandpass filter. The input circuit 36 also receives the incoming data signal between the data modulator 39 and the bandpass filter 40.

An embodiment of the subscriber telephone apparatus according to the invention operates as shown in Figures 1 and 2, wherein the speech band is in the 0.3 to 3.4 kHz, the data band is in the 0.05 to 0.3 kHz frequency band, kHz, receiving carrier frequency 12 kHz, limited carrier amplitude modulation used by the applied modulation system. The latter is a requirement due to the carrier's ability to produce multiplier demodulation by limiting.

The attenuation of the cable used for transmission depends on the length, the value of the closing impedances and the frequency. For example, 17.5 km long, 4

The damping of a symmetrical vascular pair with a diameter of 00.6 mm and a capacity of 40 nF / km is shown in Fig. 3, measured between the usual 600 Ohm and a smaller 150 Ohm closures. At higher frequencies (> 5kHz), the damping (voltage / current value) varies exponentially with length, and at low terminating resistances, the low-frequency damping approximates to DC and increases proportionally with length. The same implies a logarithmic change in length. Applying the same amount of gain control at different frequencies would result in residual attenuation being frequency dependent.

In the present invention, in the subscriber unit shown in FIG. 1, the control signal generating circuit 22 provides a different control signal to the carrier frequency amplifier 13 than to the audio frequency controlled amplifier 6. The essence of the solution is shown in Figure 4. The coupling between the input and the first output of kil is made by an ohmic resistor, and the connection between the input and the second output of ki2 is made by a diode circuit and a current mirror so that with linearly increasing input voltage, the first output kil is connected to and for the amplifier 13, and the gain changes proportional to the control current, a low frequency signal varying at the output of the control center channel B is provided at the constant carrier frequency signal (regardless of cable length) at the output of the demodulator 14 is nearly constant at the input of the controller 24 amplifier unit.

In the case of the above controller, a small amount of attenuation distortion must be ensured in the transmission direction: the increasing frequency in the audio frequency band has an increasing residual attenuation.

Therefore, in the present invention, the gain of the control amplifier 24 varies with frequency depending on the frequency. The possible construction of the control amplifier 24 is shown in FIG. At the output of the separation amplifier 41, R-C elements separate the low and high frequencies. The gain control signal only affects high frequencies, i.e., the constant gain amplifier 42 is a fixed gain, the gain gain 43 is controlled and the output signal is the sum of the two signals generated by the addition circuit 44. By adjusting the level of the signaling frequency at the upper end of the band, the central unit controls a near zero damping distortion. The 1/2 RC cut-off frequency should preferably be set to the upper edge of the band.

In order to improve the circuit stability of the telephone network and to implement other system technology aspects, it may be necessary to connect a local quad-wire subscriber system to the exchange.

-4193822

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In order to solve the above problem, the central unit of the apparatus according to the invention must be modified as shown in Fig. 6 by replacing the H "hybrid transformer and the associated line assemblies with transmitting 45 symmetry stages, receiving direction 46 asymmetry stages and a and β signal lines directly connected. to the terminals of the four-wire center.

The device according to the invention is advantageously applicable in the local area network, in particular the rural telephone network, where the subscriber's wired connection is possible but the length of the line does not allow direct connection and its quality does not allow efficient use of loop expanding and negative impedance amplifiers. The CB principle is fully accomplished, with a compelling and constant (3-4 dB) residual damping and good crosstalk characteristics. The proposed frequency assignment is compatible with current practice, and is currently using 12 kHz as a coin-receiving pulse carrier from the exchange to the subscriber.

Claims (8)

1. A very long symmetrical pair subscriber telephone apparatus having directional coupling and signaling circuits, a subscriber transmitting and receiving channel transducer, and a transmitting subscriber channel transmitting unit (A) / and the transmitting center channel mapping unit (B) providing baseband transmission, the receiving subscriber channel mapping unit (C 1) and the receiving center channel mapping unit (D) carrier frequency transmitting equipment. Apparatus according to claim 1, characterized in that a dynamic compressor (3, 34) at the input of the transmitting subscriber channel generating unit (A) and the receiving center side channel generating unit (D) is the transmitting center channel forming unit (B) and a dynamic expander (18, 26) is provided at the output of the receiving subscriber channel mapping unit (C). Device according to claim 1 or 2, characterized in that a subscriber power supply unit (T) is connected to the line on the prepaid pay side. Apparatus according to claim 1, characterized in that it has a logarithmic output (hanging) to the controlled amplifier (6) of the transmitting preamble (A) and a linear output (lin) of the receiving amplifier (13) of the receiving subscriber channel (C). ), a control signal generating circuit (22) is coupled to its reference current circuit (21). Apparatus according to claim 1 or 4, characterized in that the transmitting center-side channel-forming unit (B) comprises a control amplifier (24) having a constant transmission at low frequencies and a constant level of amplitude of the signaling frequency at high frequencies. Device according to claim 5, characterized in that in the control amplifier (24) RC circuits are connected to the isolation amplifier (41), the low-pass branch constant amplifier (42), the high-pass branch adjustable amplifier (43). 25 are connected and their output is referred to a summary (44). Apparatus according to claim 1, characterized in that the subscriber data input is transmitted through a data modulator (9) and a bandpass filter. 30 coupled to the transmit channel mapping unit (A) adder (5), via the center side data input data modulator (39) and the bandpass filter (40) to the reception center side channel mapping unit (D) adder 136), is coupled to a subscriber data output via a demodulator (C) of the receiving subscriber channel generating unit (C), via a bandpass filter (19) and a data demodulator (20), a control amplifier (24) of the transmitting center channel generator (B) 31) and is connected via a data demodulator (32) to a center-side data output. 8. Apparatus according to any one of claims 1 to 3, characterized in that in the control unit, instead of the hybrid transformer (H ') and the connecting signal wires, the stage (45) is symmetrical to the dynamic expander (26) and asymmetric to the dynamic compressor (34). There are 50 stages (46) and the signal wires (α, β) are directly connected to the terminals of the 4-wire center.