JPS625395B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides two-way transmission of signals between a center (or head) and any terminal via a transmission line using a single coaxial cable, such as in a television common reception facility. The present invention relates to communication devices.

Recently, devices installed at a school or other facility are sometimes remotely controlled from an arbitrary terminal using a common TV reception facility. The control signal is a direct current component depending on the case, and since it is not possible to directly send this signal to the television community reception facility, means are used to modulate the signal and send it using a carrier wave of a frequency that can be transmitted. FIG. 1 shows a commonly used device. 11 is a device provided in the terminal, 1 is an oscillation circuit, 5 is a control signal generation circuit, 2
3 is a modulation circuit, 3 is an amplifier circuit, 4 is an output filter, and 3 and 4 are dedicated carrier wave bands. 6 is a transmission path, 12 is a device provided at the center, 7 is an input filter, 8 is a receiving amplifier circuit, and 7 and 8 are constituted by narrow bands. 9 is a demodulation circuit whose output is applied to the controlled device 10 as a control signal.

The above devices can be controlled, but the controlled device 1
It is not possible to check whether 0 is working properly. In order to solve this problem, it is necessary to receive an operation signal from the controlled device 10 and send it back to the terminal as a confirmation signal. For this purpose, a two-way communication device is required. Furthermore, it is desirable to install a plurality of controlled devices at the center and control them simultaneously from a plurality of terminals. In this case, the communication method may be a polling method or a contention method, but since the system would be large-scale and expensive, the method shown in FIG. 2 is used as an inexpensive method. The one in FIG. 2 is an example of control from three terminals.

21, 22, and 23 are communication devices provided at the center, and 24, 25, and 26 are communication devices provided at the terminals, which may be located at different points on the transmission path 30. 2
Controlled devices 7, 28, and 29 are connected one-to-one to the devices 21, 22, and 23.

The devices 21 and 24 are in a one-to-one relationship, and are assigned a carrier frequency F ₁₀ sent from the center to the terminal and a carrier frequency F ₁₁ sent from the terminal to the center. Similarly, F ₂₀ and F ₂₁ are assigned to devices 22 and 25, and F ₃₀ and F ₃₁ are assigned to devices 23 and 26. Therefore, the controlled devices 27, 28, 29 are the terminal devices 2.
4, 25, and 26 enable independent and simultaneous control. From the viewpoint of effective use of the transmission path, carrier wave frequency settings are such that F ₁₀ , F ₂₀ , F ₃₀ are adjacent to each other, F ₁₁ , F ₂₁ ,
Place F ₃₁ adjacent.

An object of the present invention is to provide an apparatus for stably realizing the system shown in FIG. 2 at low cost, and embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 shows an embodiment of the invention. 41
is a device provided at the terminal, 50 is a device provided at the center via the transmission path 36, and 45 is a controlled device provided at the center. 31 is a relatively high frequency carrier wave (in Fig. 2
This is an oscillation circuit that generates one carrier wave corresponding to F ₁₁ , F ₂₁ , and F ₃₁ . 32 is a modulation circuit that modulates the carrier wave by the output of the control signal generation circuit 35;
3 is a narrowband amplification circuit for removing spurious waves etc. of the modulated carrier wave, and 34 is an output filter with a relatively wide band that covers the frequencies of carrier wave groups such as F ₁₁ , F ₂₁ , F ₃₁ etc. It consists of a pass filter, which allows the transmission filter to be left unadjusted. 37 selects and passes a predetermined carrier wave from among relatively low frequency carrier waves (corresponding to F ₁₀ , F ₂₀ , F ₃₀ in Figure 2) sent from the center, and passes the other carrier waves. As shown in the example of FIG. 4, this is a dedicated band filter that operates as a trap, and thereby the subsequent amplifier circuit 38 and demodulation circuit 39 can be made to have a wide band, thereby simplifying the circuit. A display circuit 40 displays an operation confirmation signal from a controlled device 45 provided at the center, and is operated by a signal obtained by the demodulation circuit 39.

On the other hand, 42 is a dedicated band filter that selects and passes relatively high-frequency carrier waves sent from the terminal device 41 and operates as a trap for the others, as in the example shown in FIG. A control signal obtained by a wideband amplification circuit 44 is a wideband demodulation circuit 44 and is sent to a controlled device 45 for control.

46 is an oscillation circuit that generates one of relatively low frequency carrier waves to be sent to the terminal device 41. 47 is a modulation circuit that modulates a carrier wave using an operation confirmation signal from the controlled device 45; 48 is a narrowband amplifier circuit for removing spurious waves from the modulated carrier wave; and 49 is an output filter _F10 . , F ₂₀ , F _{30 ,} etc., and has the same function as that in the terminal device described above.

As described above, when preparing three pairs of two-way communication devices as shown in FIG. 2, separate devices must be prepared for the carrier waves assigned to each. This has great design, manufacturing, and cost benefits, as it can be handled by creating only the oscillation circuit, its output amplification circuit, and reception filter, and preparing the same circuit for the rest. ing. Furthermore, if the carrier frequencies are placed adjacent to each other, the oscillation circuit and its output amplification circuit can be covered with a slight adjustment, and if solid-state elements are used for the receiving filter and trap, There are even greater effects on production.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a communication device in a conventional example, FIG. 2 is a block diagram of a two-way communication device in another conventional example, and FIG. 3 is a block diagram of a two-way communication device in an embodiment of the present invention. 4 and 5 are characteristic diagrams for explaining the device. 31, 46... Oscillation circuit, 32, 47... Modulation circuit, 33, 38, 43, 48... Amplification circuit, 3
4, 49... Output filter, 37, 42... Filter, 39, 44... Demodulation circuit, 40... Display device, 45... Controlled device.

Claims (1)

[Claims] 1 A two-way communication device that sends a signal using a relatively high frequency carrier wave in one direction via a coaxial cable, and a signal that uses a relatively low frequency carrier wave in the opposite direction, and is one device. consists of an oscillation circuit that generates a relatively high frequency carrier wave, a modulation circuit that modulates this carrier wave, a narrow band amplifier circuit that amplifies the modulated wave of this modulation circuit, and a relatively wide band that covers the frequencies of multiple carrier waves. and a dedicated bandpass filter that selectively passes a received relatively low frequency carrier wave and at the same time traps an arbitrary frequency.
It has a wideband amplification circuit that amplifies the selected carrier wave, and a demodulation circuit that detects the carrier wave and extracts the modulated signal, and one device passes the relatively high frequency carrier wave sent from the above-mentioned device. At the same time, a dedicated bandpass filter traps arbitrary frequencies, a wideband amplifier circuit that amplifies the selected carrier wave, a demodulation circuit that detects the carrier wave and extracts the signal, and transmits it to the above-mentioned device. an oscillation circuit that generates a carrier wave of a relatively low frequency for the purpose of the present invention, a modulation circuit that modulates this carrier wave, and a narrowband amplification circuit that amplifies the modulated wave of this modulation circuit;
A two-way communication device comprising a relatively wideband bandpass filter that covers the frequencies of a plurality of carrier waves.