JPS62261254A - Resetting circuit for catv terminal converter - Google Patents

Abstract

PURPOSE:To set a teminal converter to an initial condition and to operate the terminal converter by resetting a microcomputer for control when the input signal level of a demodulator for data communication is lowered from a specified input level. CONSTITUTION:To a CATV transmitting line, a data communicating signal is always transmitted from a center. A demodulator 3 for data communication demodulates the signal and transmits it to a microcomputer for control. The microcomputer 6 controls a terminal converter 2 based on the data. The level of an input signal (a) of the demodulator 3 is lowered to the specified input level or below, a carrier sense circuit 4 discriminates this and outputs a signal (b) to a pulse generating circuit 5. A monostable multivibrator 8 of the pulse generating circuit 5 outputs a pulse (c) of a t1 second 5V from the fall time point of the signal (b). A NAND circuit 9 outputs a signal (d) of 5V only while signals (b) and (c) are both OV. A monostable multivibrator 10 generates a resetting pulse (e) which comes to be OV for t2 seconds from the time point of the rise of the signal (d) and resets the microcomputer 6 for the control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to data communications; v! The present invention relates to a reset circuit for a CATV terminal converter that sets the terminal converter to an initial state when the input signal level of the device falls below a specified human power level for more than a certain period of time.

[Prior Art and Its Disadvantages] In a CATV system, if the data communication signal transmitted from the center to the terminal converter is interrupted, the operation of the terminal converter may become completely impossible. For example, in hotel CATV, when a check-out command is transmitted to a terminal converter, operation of the terminal converter is prohibited, but if the data communication signal is cut off due to this preferential treatment, the operation of the terminal converter is prohibited by a check-in command. cannot be canceled and you will not be able to watch television.

In addition, if unmanned operation such as station announcements,
If the data communication signal is interrupted during broadcasting, there is a drawback that it becomes impossible to operate the terminal converter, such as turning off the power, after the broadcast ends.

[Object of the Invention] The present invention has been made in view of the above points, and its purpose is to prevent the terminal converter from receiving normal data when the signal level input to the terminal converter falls below the specified input level for a certain period of time or more. An object of the present invention is to provide a reset circuit for a CATV terminal converter, which makes it possible to set the terminal converter to an initial state when the terminal converter is in an initial state.

[Summary of the Invention] The reset circuit for a CATV terminal converter of the present invention includes a demodulator for data communication, a carrier sense circuit for determining whether the input signal level to the demodulator is equal to or higher than a specified value, and the demodulator. In a CATV terminal converter that is equipped with a pulse generation circuit that outputs a reset pulse when the input signal level to the input signal drops below a specified input level for a certain period of time or more, and a control microcomputer, the output from the pulse generation circuit is The control microcomputer is reset by the generated reset pulse.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a CATV terminal converter according to the present invention. In FIG. 1, 1 is a CATV line connecting the center and terminal converters, and 2 is a terminal converter. This terminal converter 2 includes a demodulator 3 for data communication, a carrier sense circuit 4 that determines whether the input signal level to the demodulator 3 is higher than a specified value, and a carrier sense circuit 4 that determines whether the input signal level to the demodulator 3 is higher than a predetermined time. It consists of a pulse generating circuit 5 that outputs a reset pulse when the input level falls below a specified level, and a control microcomputer 6. 7 is a control microcomputer 6
This is the reset terminal.

FIG. 2 is a block diagram showing the configuration of the pulse generating circuit 5. As shown in FIG. In the figure, 8 is a first monostable multivibrator, 9 is a NAND circuit that takes the AND of the output signal of the carrier sense circuit 4 and the output signal of the first monostable multivibrator 8, and 10 is a second monostable multivibrator. It is a monostable multibibreak.

Next, the operation of the CATV terminal converter will be explained. FIG. 3 shows its operating waveform.

A data communication signal with a carrier frequency of 70.08 MHz frequency-modulated with data is constantly transmitted from the center to the CATV transmission line. A demodulator 3 for data communication demodulates the above signal and transmits the data to a control microcomputer 6
to be transmitted. The control microcomputer 6 controls the terminal converter 2 based on the above data.

This signal becomes 5V if the human power signal level a is above the specified input level, and becomes OV if it is below the specified input level.

When the input signal level of the demodulator 3 drops below the specified input level (a) in the (b) part or (c) part as shown in a, the carrier sense circuit 4 determines this and outputs the signal shown in b. is output to the pulse generation circuit 5. The pulse generating circuit 5 first detects the falling point of the signal b of the monostable multi-bi flake 8, and outputs a 5V pulse C for t1 seconds from this point.

The NAND circuit 9 takes the AND of the signals b and c, and outputs 5 pulses only while the signals c are both OV, as shown in d.

If the time for the input signal level a to fall below the specified input level (a) is less than t1 seconds as shown in part (b), the output signal d of the NAND circuit 9 will be 5V, which is not the same as the input signal level a. Due to the operation of terminal converter 2,
This is to prevent the control microcomputer 6 from being reset when the time is t1 seconds or less without any problem. The monostable multi-bibreak lO detects the rising point of the output signal d of the NAND circuit 9, generates a reset pulse e that becomes OV for t2 seconds from this point, and transmits it to the reset terminal 7 of the control microcomputer 6 for control purposes. Reset microcomputer 6. t2 is the time required to reset the control microcomputer 6. When the control microcomputer is reset, the terminal converter 2 is set to the initial state and the power switch is turned off, but after that, various switches of the terminal converter 2 can be operated.

[Effects of the Invention] As described above, according to the present invention, when the input signal level of the data communication demodulator in the CATV terminal converter drops below the specified human power level, the control microcomputer is reset. , the terminal converter can be set to an initial state and the terminal converter can be operated.

Furthermore, if necessary, all terminal converters can be reset at once by forcibly cutting off the data communication signal transmitted from the center.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of a terminal converter according to an embodiment of the present invention, Fig. 2 is a block diagram showing a pulse generation circuit used in the converter, and Fig. 3 shows operating waveforms of each part of the embodiment. be. 1... CATV transmission line, 2... terminal converter,
3... Data communication demodulator, 411. Carrier sense circuit, 5... Pulse generation circuit, 6... Control microcomputer 7... Reset terminal Applicant's agent, patent attorney Takehiko Suzue 5 Pulse generation circuit Figure 2 Figure 3 I@ゎ ψi, 7 - Michibe Uga, Commissioner of the Japan Patent Office1, Indication of the case, Patent Application No. 1983-1039202, Name of the invention, Reset circuit for CATV terminal converter 3, Person making the amendment.Relationship with the case.Patent applicant (681) Yagi Antenna Co., Ltd. 4, Agent 5, Voluntary amendment 7, Contents of amendment (1) F! AwUii page 4 jiE line 15 K r
f:y t times mJ is corrected as "NAND circuit". (2) Specification page 5 line 17 K “NAND circuit 9”
Correct the statement to read "NAND circuit 9." (3) In the second line of page 6 of the specification, the phrase "NAND circuit 9" is corrected to "NAND circuit 9." (4) On page 6, line 7 of the specification, "NAND circuit 9" is corrected to "NAND circuit 9." (5) In the second and third lines of page 7 of the specification, the phrase ``by resetting 1.'' is corrected to ``by resetting.'' (6) Figure 3 of the drawing is corrected as shown in the attached sheet. Figure 3

Claims (1)

[Claims] A demodulator for data communication, a carrier sense circuit that determines whether the input signal level to the demodulator is above a specified value, and a carrier sense circuit that determines whether the input signal level to the demodulator has fallen below the specified input level for a certain period of time or more. In a CATV terminal converter comprising a pulse generation circuit that outputs a reset pulse and a control microcomputer, the control microcomputer is reset by the reset pulse output from the pulse generation circuit. Reset circuit for CATV terminal converter.