JPS6322754B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a composite transmission circuit for simultaneously transmitting voice and data using a two-wire transmission line.

Prior art and problems Using a two-wire transmission line, such as a local telephone line,
A composite transmission method for simultaneously transmitting an audio signal and a data signal is already known. In the composite transmission system, a telephone that transmits and receives voice signals and a data modem that transmits and receives data signals that use signals in a part of the voice band are connected to the same device while eliminating mutual interference.
Requires a composite transmission circuit for coupling to wire lines.

FIG. 1 shows the general configuration of the audio data composite transmission system. In the figure, reference numeral 1 denotes a band removal filter (Rej) that blocks a part of the band A of the voice signal band, and the band A component of the voice signal from the telephone 2 is removed by the band removal filter 1. The voice band signal from the line 3 is sent to the two-wire transmission line 3, and the band removal filter 1 removes the band A component, and the signal is received by the telephone 2. Reference numeral 4 denotes a bandpass filter (BF) that passes only the above-mentioned band A signal. During data transmission, data from the data terminal 5 is converted into a band A data signal by the data modem 6, and the switch 7 It passes through the contact S side and is sent to the line 3 via the bandpass filter 4. When receiving data, the band A signal in the voice band signal from the line 3 passes through the bandpass filter 4 and passes through the contact R side of the switch 7. ,
The data is reproduced by the data modem 6 and received by the data terminal 5.

In this way, the signal from the telephone set and the signal from the data modem are combined via the band-rejection filter and the band-pass filter, respectively, and sent out to the line, and the signal from the line is sent to the band-elimination filter and the band-pass filter. The signals are then separated and received by a telephone and a data modem, respectively. However, a direct current voltage is applied to the line for power supply to the telephone, and an alternating current voltage is applied as a ringer. Both of these voltages are considerably higher than the voltages used in data modems, so band-rejection filter 1 and band-pass filter 4 must be constructed using high-voltage capacitors and coils. . on the other hand,
These filters require relatively sophisticated properties for their purpose. In other words, the band required for data signals is, for example, 2 to 2.5 KHz (abbreviated as band A in this text), and the characteristics are such that frequencies 0.2 KHz above and below this band are outside the band. Therefore, the configuration of a filter to achieve this is quite complex, but if such a filter is constructed using a high-voltage capacitor and coil, it will inevitably be large in size, and As a result, the equipment becomes larger and more expensive.

Purpose of the Invention The present invention aims to solve the problems of the prior art, and its purpose is to provide a composite transmission circuit that simultaneously transmits audio signals and data signals using a two-wire transmission line. An object of the present invention is to provide a circuit format that can reduce the size of a high-voltage filter for separating and coupling an audio signal and a data signal by simplifying the configuration of the filter.

Structure of the Invention The present invention is a composite transmission system that uses a two-wire transmission line to simultaneously transmit an audio signal and a data signal that uses a part of the audio signal band. A high-voltage low-pass filter is provided between the line and the telephone set, and a high-voltage high-pass filter that allows only audio signals to pass is provided on the input and output sides of the low-pass filter. A separation/coupling means including a band removal filter that selectively removes signals in a part of the band from the audio signal via a filter and a band pass filter that selectively passes the signal in the part of the band is connected to the audio signal. It is constructed by connecting a telephone set through a band rejection filter of the separation/coupling means and connecting the data signal transmitting/receiving means through a band pass filter.

Embodiment of the Invention FIG. 2 shows the configuration of an embodiment of the composite transmission circuit of the present invention. In this figure, the same parts as in FIG. 1 are designated by the same numbers, and 10 is a composite transmission circuit of the present invention. In the composite transmission circuit 10, 11 is a high-voltage low-pass filter (LF) that passes DC and ringer frequency signals and blocks audio frequency signals, and 12 and 13 block ringer frequency signals and block audio frequency signals. high-voltage high-pass filter (HF) that passes the signal, 14,
15 is a hybrid (H) for converting between 2-wire and 4-wire, and 16 is a separating and combining circuit for separating and combining audio signals and data signals. An example of the configuration is shown in FIG. has been done.

In FIG. 3, reference numerals 21 and 22 are band removal filters (Rej) that block signals in a part of the audio signal band A and pass signals at other audio frequencies;
23 and 24 are band pass filters (BF) that pass signals of band A and block signals of other audio frequencies; 25 is a data modem; 26 is a coupling circuit;
27 is the 4-wire side transmitting terminal (4WS), 28 is the 4-wire side receiving terminal (4WR), and 29 is the voice transmitting terminal (Voice
S), 30 is a voice receiving terminal (Voice R), and 31 is a data terminal terminal (DTE).

In FIGS. 2 and 3, the direct current and ringer signals on line 3 are sent to telephone 2 via filter 11. In FIG. On the other hand, the audio and data signals on line 3 pass through filter 12 and are applied to terminal 28 via hybrid 14. Of the signals applied to terminal 28, the voice signal passes through filter 22, terminal 30, hybrid 15, filter 13, and is received by telephone 2. Further, the data signal passes through the filter 24 and is applied to the data modem 23, where the data is reproduced and received at the data terminal 5 via the terminal 31. Conversely, the voice signal from the telephone 2 passes through the filter 13, the hybrid 15, the terminal 29, the filter 21, and is applied to the coupling circuit 26. Also, data from the data terminal 5 is sent to the terminal 31.
The data signal is applied to a data modem 25 through a filter 23, where it is converted into a data signal, and the data signal is applied through a filter 23 to a coupling circuit 26. A coupling circuit 26 couples both signals, and its output is connected to terminal 27, hybrid 1.
4, passes through a filter 12, and is sent out to a line 3.

According to the circuit configuration of the present invention shown in FIGS. 2 and 3, the DC and low frequency high voltage signals are applied to the telephone through the filter 11, but the signals are applied to the telephone through the filters 12 and 13. Therefore, the signal is not applied to the separation/coupling circuit 16. Therefore, all of the filters, data modem, etc. in the separation/coupling circuit 16 can be constructed from low voltage components. As mentioned above, band-rejection filters and band-pass filters used to separate audio and data signals require relatively complex configurations, but in the present invention these filters do not need to withstand high voltages. Therefore, it is made smaller. The separation/coupling circuit 16 can be directly applied as an audio data composite transmission device to a four-wire line in which the transmission and reception lines are independent, and since no high voltage is applied, it can be used as a single-chip or several-chip circuit.
It can be realized as an LSI, and in this case it is even more compact. On the other hand, DC and low-frequency high voltages are applied to the low-pass filter 11 and high-pass filters 12 and 13, but these filters apply DC and low-frequency high voltages, for example, 16Hz and the lower end of the audio signal to 0.3KHz. As long as it can be separated,
Even if high voltage capacitors and coils are used, the size will not increase significantly.

Effects of the Invention As explained above, the composite transmission circuit of the present invention is configured for low voltage use in a composite transmission system that simultaneously transmits an audio signal and a data signal using a two-wire transmission line. For example, a 4-wire audio data separation/coupling circuit that has been miniaturized by LSI can be applied, and a low-pass filter with a simple configuration can be used as a high-voltage filter to separate the audio signal from the DC and ringer frequencies. Since a high-pass filter can be used, the filter can be made smaller and the overall device can be made smaller.
Therefore, it is also economically advantageous.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the general configuration of an audio data composite transmission system, Fig. 2 is a block diagram showing the configuration of an embodiment of the composite transmission circuit of the present invention, and Fig. 3 is an example of the configuration of a separation/coupling circuit. FIG. 1... Band removal filter (Rej), 2... Telephone, 3... Two-wire transmission line, 4... Band pass filter (BF), 5... Data terminal, 6... Data modem, 7... Switch , 10...Composite transmission circuit of the present invention, 11...Low pass filter (LF), 1
2, 13... High pass filter (HF), 14,
15...Hybrid (H), 16...Separation and coupling circuit, 21, 22...Band removal filter (Rej),
23, 24...Band pass filter (BF), 25...
...Data modem, 26...Coupling circuit, 27...4
Line side transmission terminal (4WS), 28...4 line side reception terminal (4WR), 29...Audio transmission terminal (Voice S), 3
0...Audio reception terminal (Voice R), 31...Data terminal terminal (DTE).

Claims (1)

[Claims] 1. In a composite transmission system that uses a two-wire transmission line to simultaneously transmit an audio signal and a data signal that uses a part of the audio signal band, it is a high-voltage transmission system that allows only direct current and signals with frequencies lower than the audio signal to pass through. A low-pass filter is provided between the line and the telephone, and high-voltage high-pass filters are provided on the input and output sides of the low-pass filter to allow only audio signals to pass.The audio signal is passed through both high-pass filters. A separation/coupling means including a band removal filter that selectively removes a signal in a part of the band from the band and a band pass filter that selectively passes the signal in the part of the band is connected to the band of the separation/coupling means. A composite transmission circuit characterized in that a telephone is connected through a blocking filter and a data signal transmitting/receiving means is connected through a bandpass filter.