JPH0365072B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a branching device used, for example, in a pay television reception system, or for connecting a television signal to a
A branch that is installed on a power supply line that passes control signals for the central processing unit, and is designed to prevent other equipment from being adversely affected even if an accident occurs in the terminal equipment connected to the branch end of the branch. The purpose of the present invention is to provide a branching device for common television reception.

The drawings showing the embodiments of the present application will be described below. FIG. 1 is a system diagram showing a pay television reception system, and 1 is an antenna for receiving television waves. 2
is a VTR, which sends out tape playback signals. 3 is a modulator. 4 is a head amplifier. 5 is the main amplifier. 6
is a central processing unit that receives control signals from the terminal device 13, counts the time the television 12 is turned on, converts it into charges, and detects whether each terminal device is operating normally. 7 is a low-pass filter that passes the control signal from the terminal device 13 and blocks the television signal. 8 is a switch, and 8a is a TV connection terminal. Reference numeral 9a denotes a bidirectional amplifier, which amplifies the television signal and sends it out in the downstream direction, while passing the control signal in the upstream or downstream direction without loss. Reference numeral 9b denotes a bidirectional amplifier, which amplifies and sends out a television signal in the downstream direction and a control signal in the upstream direction. 10 is a high frequency amplifier.
A subharmonic amplifier 11 amplifies the control signal transmitted in the upstream direction. 12 is a television receiver, and switch 8
is connected to the TV connection terminal 8a. 13 is a terminal device, which is connected to the terminal device connection terminal 8b of the branch 8 and the television receiver 12;
The central processing unit 6 detects the time that the
It is used to send control signals to. 14 is a power supply line connecting each device. 15 is a connection point of the central processing unit 6.

Next, Figure 2 shows the wiring diagram of the turnout.
6 is an input terminal. 17 is an output terminal. 18 is a television connection terminal connected to the television receiver 12. Reference numeral 19 denotes a terminal device connection terminal, which is connected to the terminal device 13. 20 is a branch circuit of a well-known structure, 21 is its input terminal, 22 is its output terminal, 2
3 is the branch end. 24 is a branching circuit, 25
is its input terminal, and the branch terminal 23 of the branch circuit 20
connected to. 26 is the first branch transformer, 2
7 is its primary winding, and 28 is its secondary winding.
29 is a second branch transformer, 30 is its primary winding, and 31 is its secondary winding. 32 is a resistor for providing directionality to the branch circuit. 33 is a capacitor for passing high frequencies (TV signals) and blocking low frequencies (control signals, the frequency used is selected between DC and 100 KHz, for example). 34 is a coil for passing low frequencies (control signals) and blocking high frequencies (TV signals). 35 is a buffer resistor, which even if the terminal device connection terminal is short-circuited due to a wiring abnormality between the terminal device terminal 19 and the terminal device, other connected terminals before the input terminal 16 or after the output terminal 17 to the equipment,
This is to prevent the effects of short-circuit accidents, and its resistance value is set to a value described later.

In the above configuration, the television signal from the input terminal 16 is guided to the output terminal 17, branched by a required amount of branching, and outputted to the television connection terminal 18 via the branch end 23. On the other hand, the control signal from the terminal device connection terminal 19 is sent to both the output terminal 17 and the input terminal 16 through the buffer resistor 35. Even if the TV connection terminal 18 were to be short-circuited in such a state, since the branch circuit 20 has directionality, the effect would not affect the devices connected before the input terminal 16 and the devices connected after the output terminal 17. It is not even as good as the equipment. Furthermore, even if the terminal device connection terminal 19 is short-circuited, since the buffer resistor 35 is set to the resistance value described later, the device connected before the input terminal 16 and the device connected after the output terminal 17 There is no negative effect either.

Next, FIG. 3 shows a different wiring diagram of a branching switch, and parts having the same functions as those in FIG. 2 are given the same reference numerals with the letter "e" and redundant explanation will be omitted. Next, a branching device using the above-mentioned branching circuit will be explained with reference to FIGS. 4 and 5.

FIG. 4 shows a branching device using the circuits shown in FIGS. 2 and 3, and 37 is a flash plate. A connector 38 corresponds to the branch end 23 in the wiring diagram shown in FIG. 2, and corresponds to the branch end 23e in the wiring diagram shown in FIG. Reference numeral 39 denotes a coaxial cable plug, which corresponds to the input end 25 in the wiring diagram shown in FIG. 2, and corresponds to the input end 25e in the wiring diagram shown in FIG. 3. 40 is a coaxial cable. 4
Reference numeral 1 denotes a case in which a configuration of the branching circuit 24 shown in FIG. 2 or the branching circuit 24e shown in FIG. 3 is housed. Reference numeral 42 denotes a branch main body, which includes the branch circuit 20 shown in FIG. 2 and the branch circuit 20e shown in FIG. 3.
The following configuration is stored. (Input/output terminals are not shown.) 43 is a TV connection terminal, and 44 is a terminal device connection terminal, for which a coaxial connector or a lug terminal can be used. Figure 5 shows a branching device using the circuits shown in Figures 2 and 3.
7g is a flash plate. 43g is a TV connection terminal (outlet terminal), and 44g is a terminal device connection terminal 45 is a branch. (Input/output terminals are not shown.) Next, using Figures 6 to 8, buffer resistor 35 and
The resistance values of 35e and 35f will be explained.

Figure 6 is a wiring diagram showing an equivalent circuit for control signals in a system where a total of n branchers are used.
In the figure, E is the terminal voltage of the central processing unit 6, r
is the internal equivalent resistance of the central processing unit, R ₁ is the buffer resistance,
R ₂ represents the internal equivalent resistance of the terminal device, and E ₀ represents the terminal voltage applied to the terminal device connection terminals 19, 19e, and 19f, respectively. Note that the figure shows a state in which m terminal device connection terminals are short-circuited.

FIG. 7 is a simplified wiring diagram of FIG. 6, and the relationship between R _X1 and R _X2 shown in the figure and R ₁ and R ₂ in FIG. 7 is as follows.

R _X1 = R ₁ /m R _X2 = R ₁ + R ₂ / nm Below, the conditions for the buffer resistance R ₁ are determined.
When the circuit currents I ₁ and I ₂ are determined as shown in the figure, equations (1) and (2)
holds true.

_E =I ₁ (r+R _X1 )−I ₂ R _X1 ( ₁ ) O=−I ₁ R _X1 +I ₂ (R _X1 +R
It is shown by the formula.

E ₀ = I ₂ /n-mR ₂ (3) Solving equations (1) and (2) for I ₂ , I ₂ = R _X1・E/(R _X1 + ^R _X2 )(r+R _X1 ) _−R (4) Substituting equation (4) into equation (3), E ₀ = R ₂ E/n-m・R ₁ /m/(R ₁ /m+R ₁ +R ₂ /
n-m) (r+R ₁ /m)-(R ₁ /m) ² = R ₁ R ₂ E/m (n
-m) ・1/R ₁ r/m+(R ₁ +R ₂ )r/n-m+(R ₁
+ _R2 ) _R1 /m ₍ n-m)= _R1R2E / _R1r (n-m)+mr(
R ₁ + R ₂ ) + R ₁ (R ₁ + R ₂ ) = R ₁ R ₂ E/R ₁ ² + R ₁ (rn + R ₂ ) + mrR ₂ (5) E ₀ is a terminal device error regardless of the values of m, n, etc. Finding the condition for the difference threshold level e to be greater than ₀ , e ₀ < R ₁ R ₂ E/R ₁ ² + (rn + R ₂ ) + mrR ₂ (6) R ₁ ² + (rn + R ₂ − E/e ₀ R ₂ ) R ₁ + mrR ₂ < O (7) From formula (7), the range of R ₁ is Further, when E ₀ takes the maximum value, the optimum value of R ₁ is obtained, which is shown by equation (9).

R ₁ = 1/2 (E/e ₀ R ₂ −rn−R ₂ ) (9) Figure 8 is a chart showing the relationship between the range of buffer resistance R ₁ and the number of short-circuit terminals m. For example, if the total number of switches n = 100,
The case is shown when the internal equivalent resistance R ₂ of the terminal device is 100 kΩ, the threshold level e ₀ for malfunction of the terminal device is 1.5 V, the internal equivalent resistance r of the central processing unit is 30 Ω, and the central processing unit terminal voltage E is 5 V.

As described above, in the present invention, a branch circuit is interposed in the feeder line for transmitting television signals and control signals for the central processing unit, and a television receiver is connected to the branch end of the branch circuit. and a coil for transmitting the control signal to the central processing unit through a series circuit with a buffer resistor and a coil that passes the control signal but blocks the television signal. Because it is a device connected to a terminal device,
Even if a short circuit occurs at the branch end where the terminal equipment is connected, as is clear from the above explanation, there is no risk of adverse effects whether it is directed from the input end of the branch to the previous stage or from the output end to the subsequent stage. , which is effective in operating the central processing unit safely and accurately.

[Brief explanation of drawings]

The drawings show examples, and Fig. 1 is a system diagram of a pay TV receiving system, Fig. 2 is a wiring diagram of a turnout, Fig. 3 is a different wiring diagram of a turnout, and the diagram shown in Fig. 4 and Fig. Figure 5 is a diagram showing the turnout device, and Figure 6 is a diagram showing the turnout device.
Figure 7 is a wiring diagram showing the equivalent circuit of the system for control signals, and Figure 8 is a chart showing the relationship between the range of buffer resistance and the number of shorted terminals. 6... Central processing unit, 8... Turnout, 13...
Terminal device, 19, 19e...terminal device connection terminal,
35, 35e... buffer resistor, 41... duplexer, 4
2... Turnout main body, 44, 44g... Terminal device connection terminal, 45... Turnout.

Claims (1)

[Claims] 1. A branch circuit is installed in the feeder line for transmitting television signals and control signals for the central processing unit.
A television receiver is connected to the branch end of the branch circuit, and the central processing is connected to the branch end through a series circuit of a buffer resistor and a coil that passes the control signal but blocks the television signal. A television joint reception branch, characterized in that a terminal device for sending control signals to the device is connected.