JPH0235887A - Transmission signal processing method and its device for television interphone system - Google Patents

Abstract

PURPOSE:To improve the SN ratio of a video signal by sending the video signal of a monitor camera from a slave device with setting larger the amplification degree of a frequency band, which is easily disturbed during a transmission, and processing the amplification degree of the band after compensating it in a master device. CONSTITUTION:For the video signal of a television camera TVC of an interphone slave device B, the video signal frequency band is made to pass through by a video filter circuit 5. In a pre-emphasis circuit 6, the amplification degree of the frequency band of the interfering signal to invade on a transmission line l is set higher compared with that of the frequency band without the interfering signal. Thus, when the video signal sent from the interphone slave device B onto the signal line l reaches an interphone master device A side, a de- emphasis circuit 3 compensates a frequency characteristic G of the pre-emphasis circuit 6. Consequently, a video signal level versus an interfering signal level (SN ratio) becomes higher, the video signal is made even, simultaneously the interfering signal is suppressed, and the SN ratio is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a television intercom system, and more specifically, to a video intercom system that transmits images from an intercom slave unit having a television camera to an intercom base unit having a monitor television. The present invention relates to a signal transmission processing method and an apparatus thereof.

[Conventional technology] In order to make it possible to see visitors indoors, a television camera is installed on the side of the intercom unit installed at the entrance.
A TV intercom system, in which a monitor TV is installed on the side of the intercom base unit installed indoors so that a video can be displayed simultaneously with a call, has been developed and used.

As shown in FIG.
When the user operates the call button 200a of 00, a call signal is transmitted to the intercom main unit lOO provided in the room through the signal line p, and a ring tone is output from the speaker 100C.

When the resident picks up the handset 100a and responds, power is supplied to the television camera 200b of the child device 200, and a video signal is sent to the base device 100 through the wiring l, and is displayed as an image on the television monitor 100b. , a call is made.

FIG. 9 shows a block diagram of the configuration of this television intercom system.

This system is composed of an intercom base unit 100 installed indoors with a monitor TV TV, and an intercom slave unit 200 installed at the entrance with a monitor camera TVC. Dedicated signal lines such as coaxial cables! The slave unit 200 is connected with power from the base unit 100, and video, audio, and control signals are multiplexed and transmitted to communicate necessary information.

To explain a more specific configuration, the intercom base unit 10
0 is a variable constant current power supply @line 101.0 for supplying 'RR to the child device 200 side. an audio signal from handset H;
A modulation unit 103 that modulates a high frequency signal with a tone signal output from the tone signal generation circuit 102 by operating the alarm switch AL in an emergency. A demodulator 104 demodulates the modulated signal sent from the slave device 200 side and extracts a tone signal and a voice signal to be transmitted as a calling signal.
゜Balanced input/output circuit 105 that manually inputs the modulation signal output from the modulation section 103 and outputs the modulation signal sent from the slave device 200 side via the signal line l to the demodulation section 104.
．． The power supply current of the variable constant current power supply circuit 101 is superimposed on the modulated output of the balanced output circuit 105 to create a signal line! Twisting device 20
The modulation section 103 mixes the voice signal from the handset H and the tone signal from the tone signal generation circuit 102 in the voice/tone mixing circuit 103a. , modulation circuit 10
3b, the high frequency signal f1 serving as the first carrier is modulated by these signals, and the bandpass filter 103c is
The demodulating section 104 includes a band pass filter 104 & which selects the frequency band of the modulated signal from the balanced input/output circuit 105, and demodulates this modulated signal. a demodulation circuit 104b for decoding, a voice/tone separation circuit 104C for separating the demodulated signal into a tone signal and a voice signal according to the calling signal sent from the child device 200 side, and a voice signal amplification circuit. 104d and a tone signal amplification circuit 104e, and the output of the tone signal amplification circuit 104 is transmitted through a tone decoder 107 and a ringing signal generation circuit 108 to generate a ringing tone from the speaker SPA, and a voice signal from the voice signal amplification circuit 104d. The configuration is such that the audio from the slave device 200 side is output from the handset H by the output.

Further, the video signal transmitted from the slave device 200 side is passed through the parallel input circuit 105, amplified by the video signal amplification circuit 109, and then output to the monitor TV.

On the other hand, the other intercom slave device 200 receives an audio signal obtained by amplifying the signal from the microphone M by the microphone signal amplification circuit 201a of the modulation section 201, and outputs it from the tone signal generation circuit 202 by operating the call switch SW. 100
A modulation circuit 201C that modulates the high frequency signal f2 that is a second carrier with a tone signal that is a calling signal to the side, and a bandpass filter that limits the frequency band of the output of the modulation circuit 201C and outputs it to the balanced input/output circuit 203. 201
d, and a demodulation unit 2 that demodulates the high frequency signal sent from the base unit 100 side and extracts an emergency tone signal and audio signal.
04, and an emergency light that notifies an emergency by the output of the tone decoder 205 in accordance with the tone signal of the demodulator 204.
A balanced input/output circuit 203 receives the high frequency signal output from the modulation section 201 and the video signal output from the television camera TVC through the video filter circuit 206, and outputs the high frequency signal to the demodulation section 204; While sending out the high frequency signal to the signal line l,
A power supply separation circuit 207 for separating the internal power supply of the hanging device 200 and the power supply of the television camera TVC from the modulated signal sent from the base unit 100 side via the signal a1 via the balanced input/output circuit 203; A current detection circuit 208 that detects a power supply current sent at a constant current from 100, a supply power i
Shunt regulator 209 and current detection circuit 20 to keep the current constant
It is equipped with a camera power switch 210 that controls 0N10FF of the power supply to the VC, and the modulation section 204 includes a microphone signal amplification circuit 201 that amplifies the microphone signal to a certain level.
The output signal from a and the output signal from the tone signal generation circuit 202 are mixed by the audio/tone mixing circuit 201b and input to the modulation circuit 201c. The demodulator 204 includes a bandpass filter 204a that limits the frequency band of the high-frequency signal from the balanced input/output circuit 203; A demodulation circuit 204b for demodulating a high frequency signal, a voice/toshi separation circuit 204c for separating the demodulated signal into a tone signal and a voice signal, a voice signal amplification circuit 204d, and a tone signal amplification circuit 204.
It has a configuration with e.

In such a base unit 100 and a hanging device 200, connection terminals T1 and TG provided on the parent device 100 side and connection terminals T2 and TG provided on the hanging device side are connected to the core wire and the shield jacket wire of the coaxial cable l, respectively. The configuration is such that video, audio, and other control signals necessary for information communication are multiplexed and transmitted between the two via this signal line β.

By the way, in a system with such a configuration, when the call button SW of the hanger 200 is operated, a tone signal is output from the tone signal generation circuit 202 of the modulation section 204, and the modulation circuit 201c uses this tone signal to output the second carrier f2. FM
Modulate. The modulated second carrier f2 is sent to the base unit 100 via the balanced input/output circuit 203 and the coaxial cable l, and this FM modulated signal is sent to the base unit 100 via the balanced input/output circuit 105 of the base unit 100. When the tone signal is applied to the demodulation section 104 and FM demodulated by the demodulation circuit 104b, the tone signal is separated and outputted by the voice/tone separation circuit 104c, amplified by the tone signal amplification circuit 104e, and sent to the tone decoder 107.
A signal corresponding to the tone signal is coded and manually inputted to the calling signal generation @path 108, which causes the speaker SPA on the base unit 100 side to sound as a calling signal.

In this way, the base unit 100 that has started to groan responds with the handset H by ringing the speaker SPA, and in conjunction with picking up the handset H, a camera power control signal is input to the variable constant current power supply circuit 101. Then, in order to supply power to the television camera TVC on the hanger 200 side, its output current is switched to the maximum setting value.

Also, the audio signal of the handset H that responded above is audio/
The signal is sent from the tone mixing circuit 103a to the modulation circuit 103b to perform FM modulation on the first carrier f1. The FM-modulated first carrier f1 is transmitted from the band-pass filter 103c through the balanced input/output circuit 105 to the hanger 200 side via the coaxial cable l.

On the other hand, in the hanging device 200 that receives this signal, the signal is inputted to the demodulation circuit 204b through the balanced input/output circuit 203, the bandpass filter 204a of the demodulation section 204, and the FM demodulation wave of the first carrier is FM-demodulated to produce sound. The signal is separated and outputted by the audio/tone separation circuit 204C, amplified by the audio signal amplification circuit 204d, and sent to the speaker SP of the hanging device 200.
B outputs the response from the base unit 100 side.

Further, the constant current transmitted from the main unit 100 side is separated and outputted by the power separation circuit 207, and the current level is detected by the current detection circuit 20 days.If the current value is the maximum, a signal is sent to the camera power switch 210. is sent, and power is supplied to the television camera TVC through the shunt regulator 209.

When this television camera TVC is driven, the video signal is transmitted from the video filter circuit 206 to the balanced input/output circuit 203 and to the balanced input/output circuit 1 of the base unit 100 via the coaxial cable l.
05, the signal is amplified by the video signal amplification circuit 109 and sent to the monitor TV, where the video is displayed.

Also, the audio signal input from the microphone M of the hanging device 200 is amplified by the microphone signal amplification circuit 201a, mixed with the tone signal of the tone signal generation circuit 202 by the audio/tone mixing circuit 201b, and sent to the modulation circuit 201c. Here, the second carrier is FM-modulated and sent from the bandpass filter 201d to the balanced input/output circuit 105 between the base unit 100 and the balanced input/output circuit 105 via the coaxial cable l. , after being demodulated, is amplified by the audio signal amplification circuit 104d, and the audio is output from the handset H of the base unit 100.

And in such a TV intercom system,
The first carrier fl and the second carrier f2 are selected to have frequencies higher than the video signal frequency band of the television camera in order to prevent interference.

FIG. 10 is a diagram showing the relationship between these frequencies, and shows the relationship between the DC power supply voltage, the video signal having a frequency band of several MHz, and the main unit modulation wave by the first carrier f1 at a higher frequency. The suspension modulated waves by the second carrier f2 are set to different frequencies and are multiplexed and transmitted through the dedicated Q signal line.

FIG. 11 is a diagram showing the relationship between frequencies of signals before modulation of the base unit modulated wave and the hanger modulated wave. In other words, the audio signal has a frequency band of approximately 10KHz, and the tone signal transmitted at the same time has a frequency band of approximately 20KHz, which is outside the audio signal band.
Hz to prevent interference.

By the way, in such a TV intercom system, the signal line l is installed between the hanging device 200 installed at the entrance and the base unit 100 installed indoors, but as the extension distance of the signal line l becomes longer, , it is easy for external noise to enter the signal line l, and in particular, when broadcast radio waves, amateur radio waves, or radio signals generated from a car's ignition system are induced on the signal line β, they become interference noise in the video signal band, The image will be obstructed and you will not be able to get a clear image.

Therefore, the most effective measure against such interference is to shorten the extension distance of signal line l, but if you limit the extension distance of signal line β, you will naturally limit the number of residential units in which a TV intercom system can be installed. It will be done.

In addition, if the extension distance of the signal line 1 must be increased, measures are taken to eliminate common mode noise such as interference waves by increasing the electrical balance of the signal line 2. There is a limit to how much interference can be eliminated, especially when connecting video, audio, and power to a pair of signal lines! In the case of a TV intercom system that transmits power via a signal line L, a power superimposition circuit is added to the signal line L to transmit power, so it is very difficult to obtain the required balance, and it is necessary to extend the signal line L. There is a need for measures that can provide clear images by reducing the level of external noise even when the distance is long.

Furthermore, apart from such interference radio waves, as the length of the signal line l increases, the video signal will attenuate due to the resistance component of the signal line l itself, so in order to ensure the necessary video signal level, it is necessary to Limit the signal line β to be used when installing a TV intercom in
It becomes necessary to take measures to bring the temperature within the specified value.

However, it is time-consuming to measure the extension distance of the signal line l during construction, and the length of the signal line β is limited, which naturally limits the number of residential units in which the signal line can be installed. It is desired to develop a television intercom system that can be easily installed regardless of the length of the signal line by compensating for signal attenuation in the signal line β even when the length of the line 1 is long.

[Problems to be Solved by the Invention] The present invention is proposed in order to solve the above-mentioned problems inherent in intercom systems. An object of the present invention is to provide a signal processing method in a television intercom system that can result in a video signal with less noise even if interference waves are induced therein, and an apparatus for implementing the processing method.

[Means for Solving the Problems] The signal processing method of the present invention proposed to achieve the above object is to connect an intercom base unit having a monitor television and an intercom hanger having a monitor camera with a dedicated signal. In a TV intercom system that is connected by a wire and transmits video signals, the intercom hanger transmits the video signal output from the monitor camera by preventing interference during the transmission of the signal wire in the entire frequency band. While the intercom main unit that receives the video signal via the transmission line sets the amplification degree high in the frequency band that is easily received, the intercom slave unit sets the amplification degree high in the received video signal's entire frequency band. It is characterized in that processing is performed after compensating for the amplification degree of the increased band.

In addition, in the device of the present invention proposed to realize the above signal processing method, the intercom hanger is equipped with a frequency band that is susceptible to interference during transmission of the above signal line, out of the entire frequency band of the video signal of the monitor camera. The present invention is characterized in that a pre-emphasis circuit with a high degree of amplification is provided, and the intercom base unit is provided with a de-emphasis circuit that compensates for frequency characteristics caused by the pre-emphasis circuit.

Furthermore, the device of the present invention proposed at the same time is characterized by a configuration in which the transmission loss of the video signal on the signal line is compensated for by a voltage control amplifier circuit provided on the intercom base unit side, and a desirable aspect of this device is In this case, the amplification degree of the voltage-controlled amplifier circuit is configured to be controlled by the output voltage of a variable constant current power supply circuit that changes the output voltage in accordance with the length of the signal line provided on the intercom base unit side. ing.

[Function] In the signal processing method of the present invention, the video signal from the monitor camera of the intercom hanger is such that the degree of amplification in the frequency band that is interfered with during transmission of the signal line is greater than in the frequency band that is not interfered with. Out of the total frequency band of the received video signal, the intercom base unit compensates for the amplification of the frequency band that was amplified on the intercom slave side, flattening the frequency characteristics. It will be returned and then processed.

In addition, in the television intercom device of the present invention, the video signal of the monitor camera of the intercom hanger is amplified in the pre-emphasis circuit in the frequency band that is interfered with by the signal line compared to the frequency band that is not interfered with.
On the other hand, in the intercom base unit, a de-emphasis circuit lowers the amplification degree of the frequency band affected by interference to flatten the frequency characteristics of the video signal before processing.

In addition, in the device of the present invention proposed at the same time, the amplification degree of the voltage control amplifier provided on the intercom base unit side increases when the signal line is long and the transmission loss is large, thereby preventing a drop in the video signal level.

In this preferred embodiment, the length of the signal line is detected by the output voltage of the variable constant current power supply circuit provided on the base unit side, and the amplification degree of the voltage control amplifier is controlled by this output voltage, and the length of the signal line is detected. Transmission loss caused by this is compensated for.

[Example] The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a schematic basic configuration diagram of the apparatus of the present invention.

The video signal frequency band of the video signal from the TV camera TVC of the intercom hanger B is selectively passed through the video filter circuit 5, and the pre-emphasis circuit 6 determines the amplification degree of the frequency band of the interference signal that enters the transmission line β. The frequency band is amplified with a higher degree of amplification than the frequency band that does not exist.

In this way, when the video signal sent from the intercom hanger B onto the signal line β reaches the intercom base unit A side, the de-emphasis circuit 3 de-emphasis circuit 6
Since the frequency characteristic G of is amplified by the video signal amplification circuit 4, and the video is displayed on a monitor TV.

Further, in the second aspect of the present invention, since the principle that the power supply voltage output from the variable constant current power supply port 91 of the base unit A increases as the extension distance of the signal line l becomes longer is utilized, the signal line p When the transmission loss at the signal line β is L, the amplification degree of the voltage control amplifier 2 is controlled by the output voltage of the variable constant current power supply circuit 1, and the transmission loss at the signal line β is reduced by increasing it by L over the entire frequency band. is automatically compensated for, and a video signal at a required level is always supplied to the video signal amplification circuit 4.

FIGS. 2a and 2b are diagrams explaining the process of suppressing interference waves by the method of the present invention, and FIG. 2a shows a conventional signal processing method.

In the conventional signal processing method, as shown in FIG. 2a (a), an interference signal N is superimposed on the video signal S from the intercom hanger B during transmission on the signal line l, and the interference signal N is superimposed on the video signal S from the intercom parent WA side. As shown in Figure (b), since the signal is amplified as it is, the S/N ratio between the video signal and the interference signal is not improved at all.

However, in the method of the present invention, the video signal sent from the slave device B side is amplified by increasing the amplification degree from a frequency fS lower than the lowest frequency fn of the interference signal generated during transmission on the signal line l. , the video signal S is transmitted on the signal line l with the frequency characteristics shown in Fig. 2b (a), and the receiving unit A side compensates for the above-mentioned amplification on the hanging device side. , the amplification degree of high frequencies is reduced and the video signal returns to a flat frequency characteristic, and at the same time, the interfering signal is also reduced, and the S/N ratio is improved as shown in Figure 2b (b). Become.

FIG. 3 shows an example of a pre-emphasis circuit used in the present invention.

The circuit shown in FIG. 3(a) consists of a resistor R1 and a capacitor CI
A resistor R2 is connected to a parallel circuit as shown in the figure, and a video signal S from a television camera of the hanger B is applied to an input terminal TI, and an output is obtained from an output terminal T2.

This circuit has frequency characteristics as shown in the figure (b), and has a turnover frequency fl (fl=1/(2×πX
RIXCI)) and roll-off frequency f2 (f2=1/
(2X (R1//R2)
10ct). Therefore, the video signal S is amplified with this frequency characteristic and the signal &I
It will be sent to n.

On the other hand, FIG. 4(a) shows an example of a de-emphasis circuit, which is constructed by connecting a capacitor c2 in parallel to a resistor R4 of a voltage dividing circuit of resistors R3 and R4 as shown in the figure. The video signal S transmitted via the line 1 is applied to the input terminal T3, and an output is obtained from the output terminal T4.

The frequency characteristics of this de-emphasis circuit are as shown in the same figure (b), and the roll-off frequency fl (f 1 = 2
XπX ((R3//R4) Therefore, by setting the circuit constants so that the turnover frequency fl of the pre-emphasis circuit and the roll-off frequency fl of the de-emphasis circuit are the same, the video signal passes through the pre-emphasis circuit and the de-emphasis circuit. , will have the original flat frequency characteristics.

Further, FIG. 5 shows an example of the internal circuit of the base unit. In the figure, the de-emphasis circuit 3 is composed of the de-emphasis element 4a, the amplifier AMP2 and the resistor R5, but the amplifier AMP2 and the resistor R5 can be omitted depending on the circuit design.

In this embodiment, an amplifier AMPI is connected in parallel to the input terminal T3' and the output terminal T4' of the de-emphasis circuit 3.
A voltage control amplifier 2 consisting of a resistor R6, an FET, and a Q is provided, and a variable constant current circuit 1 is connected to the voltage control amplifier 2.
The output voltage of
In addition to the voltage control amplifier 2 by dividing the voltage by a, the amplification degree of the de-emphasis circuit 3 is controlled to compensate for transmission loss in the signal line l.

In this circuit, as the transmission distance becomes longer, as shown in FIG. 6(a), the output voltage of the variable constant current power supply circuit 1 of the base unit A increases, and the Since power is applied to the gate, as the transmission distance increases, the output voltage also increases at the same time, and as shown in Figure 6(b), the FET
, since the equivalent resistance between the train and source of Q decreases,
The voltage division ratio with the resistor R6 increases and the amplification degree increases, and as a result, the amplification degree is controlled to increase in response to the transmission loss (see FIG. 6(C)).

FIG. 7 is a block diagram showing the configuration of a television intercom system to which the device of the present invention is applied.

In the figure, since everything other than the gist of the present invention is the same as the conventional system, the explanation thereof will be omitted.

In this system, a video signal from the TV camera TVC of the hanging device B is passed through a video filter 5, a pre-emphasis circuit 6 amplifies a predetermined band of the video signal, and then passes through a balanced input/output circuit 7 to a signal line! will be sent to.

In the rA machine A, the video signal from the signal line 1 is input to the de-emphasis circuit 3 through the balanced input/output circuit 8, and after the frequency characteristics of the video signal are flattened, the video signal is sent to the video signal amplification circuit 4.
The image is amplified and displayed on a TV monitor.

Further, the output voltage of the variable constant current power supply circuit 1, which changes depending on the length of the signal line l, has its amplification degree controlled by the voltage control amplifier 2 to compensate for transmission loss in the signal line β.

In the above embodiment, the de-emphasis circuit 3 and the voltage-controlled amplifier 2 are connected in parallel, but it is also possible to connect the de-emphasis circuit 3 and the voltage-controlled amplifier 2 in series.

[Effects of the Invention] According to the signal processing method and device of the present invention, the level of interference waves induced on the signal line connected between the intercom hanger and the intercom base unit is suppressed on the base unit side. ,
The S/N ratio of the video signal is improved, making it possible to obtain clear video.

In addition, in the device of the present invention proposed at the same time, the amplification degree of the de-emphasis circuit on the base unit side is controlled according to the transmission loss in the signal line, so even if the signal line is long, a stable video signal level can always be obtained. Furthermore, in the device related to the invention, by detecting the length of the signal line using the output voltage of the variable constant current circuit, transmission loss when the signal line becomes long is compensated for, thereby improving reliability. We are able to supply high quality TV intercom systems.

[Brief explanation of the drawing]

Figure 1 is a circuit configuration diagram for carrying out the method of the present invention, Figures 2a and 2b are diagrams explaining the principle of the method of the present invention, and Figures 3 to 6 are specific examples of circuits used in the apparatus of the present invention. 6 is an explanatory diagram of its operation, FIG. 7 is a block diagram of a television intercom system incorporating the present invention, FIG. 8 is an explanatory diagram of a conventional television intercom system, and FIG. 9 is a block diagram showing its configuration. , FIG. 1O, and FIG. 11 are explanatory diagrams showing the relationship between the transmission frequencies. [Explanation of codes A...Intercom base unit TV...Monitor TV B...Intercom slave unit TVC...Monitor camera! ... Signal line 1 ... Variable constant current tt1 circuit 2 ... Voltage control amplifier 3 ... De-emphasis circuit 6 ... Pre-emphasis circuit

Claims (4)

[Claims] (1) In a television intercom system in which a video signal is transmitted by connecting an intercom base unit with a monitor TV and an intercom slave unit with a monitor camera using a dedicated signal line, the intercom slave unit has a monitor camera. The video signal output from the monitor camera is sent out by setting a large amplification degree in the frequency band that is susceptible to interference during transmission on the signal line, while transmitting the video signal through the transmission line. In a TV intercom system, the intercom base unit that receives the signal processes the received video signal after compensating for the amplification degree of the band where the amplification degree is increased on the intercom slave side among the entire frequency band of the received video signal. transmission signal processing method. (2) In a TV intercom system in which a video signal is transmitted by connecting an intercom base unit with a monitor TV and an intercom slave unit with a monitor camera through a dedicated signal line, the intercom slave unit has a monitor camera. teeth,
A pre-emphasis circuit is provided that increases the degree of amplification of the frequency band that is susceptible to interference during transmission of the signal line out of the entire frequency band of the video signal of the monitor camera, and the intercom base unit is equipped with the pre-emphasis circuit. A television intercom system characterized by being equipped with a de-emphasis circuit that compensates for frequency characteristics caused by. (3) In a TV intercom system in which a video signal is transmitted by connecting an intercom base unit with a monitor TV and an intercom slave unit with a monitor camera through a dedicated signal line, the video on the signal line is A television intercom system characterized by having a configuration in which signal transmission loss is compensated for by a voltage control amplifier circuit provided on the intercom base unit side. (4) A configuration in which the amplification degree of the voltage control amplifier circuit is controlled by the output voltage of a variable constant current power supply circuit that changes the output voltage in accordance with the length of the signal line provided on the intercom base unit side. 4. The television intercom system according to claim 3.