CA1076651A - Blanker inhibit circuit - Google Patents
Blanker inhibit circuitInfo
- Publication number
- CA1076651A CA1076651A CA271,698A CA271698A CA1076651A CA 1076651 A CA1076651 A CA 1076651A CA 271698 A CA271698 A CA 271698A CA 1076651 A CA1076651 A CA 1076651A
- Authority
- CA
- Canada
- Prior art keywords
- radio frequency
- blanker
- inhibit
- frequency signals
- automatic gain
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/3052—Automatic control in amplifiers having semiconductor devices in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
- H03G3/20—Automatic control
- H03G3/30—Automatic control in amplifiers having semiconductor devices
- H03G3/34—Muting amplifier when no signal is present or when only weak signals are present, or caused by the presence of noise signals, e.g. squelch systems
- H03G3/345—Muting during a short period of time when noise pulses are detected, i.e. blanking
Abstract
BLANKER INHIBIT CIRCUIT
ABSTRACT
A radio receiver includes a blanker circuit for muting the receiver in response to interfering noise signals. The invention contemplates a transistor switch which, when biased to its nonconducting state, inhibits blanker action.
The transistor is biased to nonconduction when the receiver provided automatic gain control (AGC) level is below the threshold voltage of the transistor. An adjustment is provided for controlling the AGC level at which blanker inhibit is introduced. Temperature compensating circuitry maintains inhibit action response at the threshold voltage with changes in ambient temperature.
ABSTRACT
A radio receiver includes a blanker circuit for muting the receiver in response to interfering noise signals. The invention contemplates a transistor switch which, when biased to its nonconducting state, inhibits blanker action.
The transistor is biased to nonconduction when the receiver provided automatic gain control (AGC) level is below the threshold voltage of the transistor. An adjustment is provided for controlling the AGC level at which blanker inhibit is introduced. Temperature compensating circuitry maintains inhibit action response at the threshold voltage with changes in ambient temperature.
Description
BACKGROUND OF THE INVENTION
The present invention pertains to the radio receiver art and, more particularly, to improved blanker circuitry for use in a radio receiver.
Blanking circuits for use in communication radio re-;~ ceivers are well known in the art. Generally, the blanker circuits detect noise signals, introduced by the transmittingmedium, which are received along with transmitted information signals. Several means for detecting the noise signal have been devised. A common method is to assume that received signals above a given level are noise. The detected noise signals are processed whëreby a blanking signal is produced, which blanking signal mutes the output of the receiver for the duration of the blanking signal, thus preventing an annoying noise burst from being heard by the listener.
, . .
., .
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. - : :
.
5~
A problem with conventional noise blanking circuits has been that when the received information signal exceeds a threshold level the action of the noise blanker becomes very annoying. That is, a listener prefers to hear a strong information signal along with noise signals, rather than the distracting "holes" caused by the blanker chopping the re-ceived signal.
_MMARY OF TH~ INVENTION
It is an object of this invention, therefore, to provide a means for inhibiting blanker circuit action for received signals exceeding a given threshold level.
Briefly, according to the invention, the blanking means - is intended for use in conjunction with a radio receiver, which receiver includes a means to receive and process radio frequency sign~ls , e.g. an antenna and tuner. The blanking means includes a blanker circuit which detects noise pulses in the radio frequency signal, blanking the receiver in response thereto. An inhibit means inactivates the blanker circuit in response to the radio frequency signals exceeding a predetermined threshold level. The inhibit means may also include a means for adjusting the predetermined threshold level and a means for temperature compensating the inhibit means response to the predetermined threshold level whereby proper inhibit action occurs over a temperature range.
More particularly, there is provided:
An AM radio receiver including means for receiving radio frequency signals; tuner means for processing the received radio frequency signals and producing audio output signals in response thereto, the tuner means also producing an automatic gain control signal having a level representative of the magnitude of the received radio frequency signals; a blanker _2~
1~ 7 ~ 51 circuit for detecting noise pulses in the received radio frequency signals and blankin~ the tuner means in response thereto;- and inhibit means for inactivating the blanker cir-- cuit responsive to the automatic gain control signal assuming a predetermined level corresponding to a minlmum received radio frequency signal level, whereby when the received radio frequency signals exceed the minimum value the inhibit means i~activates the blanker ci~cuit.
BRIEF DESCRIPTION OF T~E DRAWING
The single drawinq illustrates, in .schematic diagram form, the preferred embodiment of the blanker inhibit cir~uit when used in combination with a conventional amplitude. du-lated radio receiver.
-2a-107f~f~51 DESCRIPTION OF THE PRE~ERRED
-EMBODIMENT OF THE INVENTION
Referring to the attached figure, a conventional amplitude modulated radio receiver 10 is shown in combination with the blanXer inhibit circuit 12 of the invention. The radio re-ceiver 10 includes an antenna 11 for receiving transmitted radio frequency signals. ~lso received by the antenna 12 are noise signals commonly introduced by the transmitting medium. Signals from the antenna 11 are fed to a radio frequency amplifier stage 14. Such stages generally include tuning circuitry fox tuning the receiver to an appropriate channel or station~ The output of the radio frequency amplifier 14 feeds to one input of a mixer stage 16. The mixer has a second input to which is applied a signal from a local oscillator 18. Operating in the conventional manner, the mixer 16 converts the received radio frequency signal from radlo fre~uency ampliier 14 to an intermediate frequency.
A blanker gate 20 couples from the output of the mixer 16 to the input of an intermediate frequency filter and amplifier stage 22. The blanker gate, in normal operation, passes intermediate frequency signals from the mixer 16 to the intermediate frequency amplifier 22. However, in response to a blanking signal received at its blanking signal input 24, the blanker gate decouples the mixer 16 from the inter-mediate frequency stage 22 thereby muting the receiver.
While any of a number of blanker gate 20 designs are available, the preferred embodiment of the invention contemplates incorporation of the blanker gate described in co~ending patent application S-erial No. 272,182, filed February 21, 1977, invented by James Wilson Rae and Larry Wright, and assigned to the same assignee as the instant application.
~2 - 3 -- lO'~ Sl The intermediate frequency signal is filtered and amplified in the intermediate frequency stage 22 and there-after passed to a detector stage 26.
The intermediate frequency filter and amplifier 22 produces an automatic gain control (AGC) signal at its AGC
- output terminal 23. This signal is fed back to a gain control terminal 15 in the RF amplifier for controlling the gain thereof. This AGC signal has an amplitude representative of the level of received radio frequency signals. In this particular em~odiment, as the amplitude of the radio fre~uency signals increases the produced AGC voltage decreases propor-tionally. Such AGC systems are well known in the radio receiver art.
The detector stage is of common design whereby it produces at its output the recovered audio information signal from the amplitude modulated intermediate frequency signal. The audio signal is amplified in audio amplifier 28 and transduced to audibility in speaker 30.
The antenna 11 also feeds to a second radio frequency amplifier 32 which constitutes the input of a blanking circuit. The radio frequency amplifier 32 prevents loading of the blanker circuit on the receiver 10 tuning stage, and provides amplification to the antenna 11 signals. The amplified signals are passed to a blanking signal generator 34 which operates in the known manner to extract the noise signals and produce an appropriate blanking signal. While any of a number of blanking signal generators may be employed, a particularly effective generator may be found in United Kingdom Patent No. 1,540,793 dated February 25, 1977 invented by James W. Rae and James Andrews, and assigned to the same assignee as the present application. These blanking _ 4 _ 1~76651 signals are in turn fed to the blanking signal input 24 of the blanker gate 20.
The radio frequency amplifier 32 has a control input terminal 36. In response to a low voltage at control input 36, the radio frequency amplifier stage 32 passes signals to the blanking signal generator 34. However, when the voltage at control input 36 assumes a high value, the radio frequency signals are no longer passed by the radio frequency amplifier 32, whereby the blanking circuit is inhibited. While many techniques are known in the art for providing the controlled radio frequency amplifier 32, a particularly useful radio frequency amplifier having a control input 36 is the MC 1350 integrated circuit manufactured by Motorola, Inc. In the MC
1350 integrated circuit, a control signal may be applied to pin 5 to control the amplifier operation.
Coupled to the control input 36 of radio frequency amplifier 32 is the blanker inhibit circuit 12. The blanker inhibit circuit 12 is comprised of a bipolar semiconductor transistor 40 having its base connected through a limiting resistor 42 to the AGC output 23 of the intermediate frequency filter and amplifier 22, its emitter coupled to a potentiometer 44 to ground potential, and its collector coupled both to the control input 36 of radio frequency amplifier 32 and through a load resistor to a source of DC bias, or B+
potential. The remaining free end of potentiometer 44 is connected through a temperature compensating diode 48 to the B~ DC supply.
Operation of the blanker inhibit circuit 12 may be understood as follows. For received radio frequency signals below a minimum threshold level, the AGC voltage from the intermediate frequency filter and amplifier 22 is of sufficient : .:
1~7f~;~iSI
magnitude to bias the transistor switch 40 to a conducting stage such that the control input 36 of the radio frequency amplifier 32 is at a low level. Thus, in this mode, the blanking circuit operates in its normal mode. However, for recelved radio frequency signals exceeding a threshold level, the AGC voltage at the output terminal 23 of the intermediate frequency filter and amplifier 22 is insufficient to bias the transistor 40 to its conductive state, resulting in the voltage at control terminal 36 assuming a high level.
This inhibits further blanker circuit action.
By appropriately adjusting the potentiometer 44, the level of received radio frequency signals at which the blanker inhibit occurs can be precisely determined. Also, the voltage drop across the temperature compensating diode 48 compensates for the base to emitter voltage change in the switching transistor 40 such that the desired threshold level of the blanker inhibit circuit 12 may be maintained over an ambient temperature range.
In summary, a blanker inhibit circuit has been described which precisely inhibits the blanking action in a radio fre-quency receiver for received radio frequency signals exceeding a minimum threshold level. Means have been described for adjusting the threshold level, and for temperature compensating the same.
While the preferred embodiment of the invention has been described in detail, it should be apparent that many modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention.
The present invention pertains to the radio receiver art and, more particularly, to improved blanker circuitry for use in a radio receiver.
Blanking circuits for use in communication radio re-;~ ceivers are well known in the art. Generally, the blanker circuits detect noise signals, introduced by the transmittingmedium, which are received along with transmitted information signals. Several means for detecting the noise signal have been devised. A common method is to assume that received signals above a given level are noise. The detected noise signals are processed whëreby a blanking signal is produced, which blanking signal mutes the output of the receiver for the duration of the blanking signal, thus preventing an annoying noise burst from being heard by the listener.
, . .
., .
- . ~,.
.~ ~
, , .
~. .: ~ ~ . ; . , : ~ ~
. - : :
.
5~
A problem with conventional noise blanking circuits has been that when the received information signal exceeds a threshold level the action of the noise blanker becomes very annoying. That is, a listener prefers to hear a strong information signal along with noise signals, rather than the distracting "holes" caused by the blanker chopping the re-ceived signal.
_MMARY OF TH~ INVENTION
It is an object of this invention, therefore, to provide a means for inhibiting blanker circuit action for received signals exceeding a given threshold level.
Briefly, according to the invention, the blanking means - is intended for use in conjunction with a radio receiver, which receiver includes a means to receive and process radio frequency sign~ls , e.g. an antenna and tuner. The blanking means includes a blanker circuit which detects noise pulses in the radio frequency signal, blanking the receiver in response thereto. An inhibit means inactivates the blanker circuit in response to the radio frequency signals exceeding a predetermined threshold level. The inhibit means may also include a means for adjusting the predetermined threshold level and a means for temperature compensating the inhibit means response to the predetermined threshold level whereby proper inhibit action occurs over a temperature range.
More particularly, there is provided:
An AM radio receiver including means for receiving radio frequency signals; tuner means for processing the received radio frequency signals and producing audio output signals in response thereto, the tuner means also producing an automatic gain control signal having a level representative of the magnitude of the received radio frequency signals; a blanker _2~
1~ 7 ~ 51 circuit for detecting noise pulses in the received radio frequency signals and blankin~ the tuner means in response thereto;- and inhibit means for inactivating the blanker cir-- cuit responsive to the automatic gain control signal assuming a predetermined level corresponding to a minlmum received radio frequency signal level, whereby when the received radio frequency signals exceed the minimum value the inhibit means i~activates the blanker ci~cuit.
BRIEF DESCRIPTION OF T~E DRAWING
The single drawinq illustrates, in .schematic diagram form, the preferred embodiment of the blanker inhibit cir~uit when used in combination with a conventional amplitude. du-lated radio receiver.
-2a-107f~f~51 DESCRIPTION OF THE PRE~ERRED
-EMBODIMENT OF THE INVENTION
Referring to the attached figure, a conventional amplitude modulated radio receiver 10 is shown in combination with the blanXer inhibit circuit 12 of the invention. The radio re-ceiver 10 includes an antenna 11 for receiving transmitted radio frequency signals. ~lso received by the antenna 12 are noise signals commonly introduced by the transmitting medium. Signals from the antenna 11 are fed to a radio frequency amplifier stage 14. Such stages generally include tuning circuitry fox tuning the receiver to an appropriate channel or station~ The output of the radio frequency amplifier 14 feeds to one input of a mixer stage 16. The mixer has a second input to which is applied a signal from a local oscillator 18. Operating in the conventional manner, the mixer 16 converts the received radio frequency signal from radlo fre~uency ampliier 14 to an intermediate frequency.
A blanker gate 20 couples from the output of the mixer 16 to the input of an intermediate frequency filter and amplifier stage 22. The blanker gate, in normal operation, passes intermediate frequency signals from the mixer 16 to the intermediate frequency amplifier 22. However, in response to a blanking signal received at its blanking signal input 24, the blanker gate decouples the mixer 16 from the inter-mediate frequency stage 22 thereby muting the receiver.
While any of a number of blanker gate 20 designs are available, the preferred embodiment of the invention contemplates incorporation of the blanker gate described in co~ending patent application S-erial No. 272,182, filed February 21, 1977, invented by James Wilson Rae and Larry Wright, and assigned to the same assignee as the instant application.
~2 - 3 -- lO'~ Sl The intermediate frequency signal is filtered and amplified in the intermediate frequency stage 22 and there-after passed to a detector stage 26.
The intermediate frequency filter and amplifier 22 produces an automatic gain control (AGC) signal at its AGC
- output terminal 23. This signal is fed back to a gain control terminal 15 in the RF amplifier for controlling the gain thereof. This AGC signal has an amplitude representative of the level of received radio frequency signals. In this particular em~odiment, as the amplitude of the radio fre~uency signals increases the produced AGC voltage decreases propor-tionally. Such AGC systems are well known in the radio receiver art.
The detector stage is of common design whereby it produces at its output the recovered audio information signal from the amplitude modulated intermediate frequency signal. The audio signal is amplified in audio amplifier 28 and transduced to audibility in speaker 30.
The antenna 11 also feeds to a second radio frequency amplifier 32 which constitutes the input of a blanking circuit. The radio frequency amplifier 32 prevents loading of the blanker circuit on the receiver 10 tuning stage, and provides amplification to the antenna 11 signals. The amplified signals are passed to a blanking signal generator 34 which operates in the known manner to extract the noise signals and produce an appropriate blanking signal. While any of a number of blanking signal generators may be employed, a particularly effective generator may be found in United Kingdom Patent No. 1,540,793 dated February 25, 1977 invented by James W. Rae and James Andrews, and assigned to the same assignee as the present application. These blanking _ 4 _ 1~76651 signals are in turn fed to the blanking signal input 24 of the blanker gate 20.
The radio frequency amplifier 32 has a control input terminal 36. In response to a low voltage at control input 36, the radio frequency amplifier stage 32 passes signals to the blanking signal generator 34. However, when the voltage at control input 36 assumes a high value, the radio frequency signals are no longer passed by the radio frequency amplifier 32, whereby the blanking circuit is inhibited. While many techniques are known in the art for providing the controlled radio frequency amplifier 32, a particularly useful radio frequency amplifier having a control input 36 is the MC 1350 integrated circuit manufactured by Motorola, Inc. In the MC
1350 integrated circuit, a control signal may be applied to pin 5 to control the amplifier operation.
Coupled to the control input 36 of radio frequency amplifier 32 is the blanker inhibit circuit 12. The blanker inhibit circuit 12 is comprised of a bipolar semiconductor transistor 40 having its base connected through a limiting resistor 42 to the AGC output 23 of the intermediate frequency filter and amplifier 22, its emitter coupled to a potentiometer 44 to ground potential, and its collector coupled both to the control input 36 of radio frequency amplifier 32 and through a load resistor to a source of DC bias, or B+
potential. The remaining free end of potentiometer 44 is connected through a temperature compensating diode 48 to the B~ DC supply.
Operation of the blanker inhibit circuit 12 may be understood as follows. For received radio frequency signals below a minimum threshold level, the AGC voltage from the intermediate frequency filter and amplifier 22 is of sufficient : .:
1~7f~;~iSI
magnitude to bias the transistor switch 40 to a conducting stage such that the control input 36 of the radio frequency amplifier 32 is at a low level. Thus, in this mode, the blanking circuit operates in its normal mode. However, for recelved radio frequency signals exceeding a threshold level, the AGC voltage at the output terminal 23 of the intermediate frequency filter and amplifier 22 is insufficient to bias the transistor 40 to its conductive state, resulting in the voltage at control terminal 36 assuming a high level.
This inhibits further blanker circuit action.
By appropriately adjusting the potentiometer 44, the level of received radio frequency signals at which the blanker inhibit occurs can be precisely determined. Also, the voltage drop across the temperature compensating diode 48 compensates for the base to emitter voltage change in the switching transistor 40 such that the desired threshold level of the blanker inhibit circuit 12 may be maintained over an ambient temperature range.
In summary, a blanker inhibit circuit has been described which precisely inhibits the blanking action in a radio fre-quency receiver for received radio frequency signals exceeding a minimum threshold level. Means have been described for adjusting the threshold level, and for temperature compensating the same.
While the preferred embodiment of the invention has been described in detail, it should be apparent that many modifications and variations thereto are possible, all of which fall within the true spirit and scope of the invention.
Claims (5)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An AM radio receiver including means for receiving radio frequency signals; tuner means for processing the received radio frequency signals and producing audio output signals in response thereto, the tuner means also producing an automatic gain control signal having a level representative of the magnitude of the received radio frequency signals; a blanker circuit for detecting noise pulses in the received radio frequency signals and blanking the tuner means in response thereto; and inhibit means for inactivating the blanker cir-cuit responsive to the automatic gain control signal assuming a predetermined level corresponding to a minimum received radio frequency signal level, whereby when the received radio frequency signals exceed the minimum value the inhibit means inactivates the blanker circuit.
2. The radio receiver of claim 1 wherein the inhibit means comprises a means for adjusting the automatic gain con-trol predetermined level.
3. The radio receiver of claim 1 wherein the blanker circuit comprises a radio frequency amplifier for amplifying the received radio frequency signals and passing them to a subsequent blanker circuit stage, and the inhibit means in-cludes switch means coupled to the radio frequency amplifier, the switch means operable to inhibit the radio frequency ampli-fier from passing the amplified received radio frequency signals to the subsequent blanker circuit stage responsive to the automatic gain control signal assuming the predetermined level.
4. The radio receiver of claim 3 wherein the switch means is comprised of a semiconductor device.
5. The radio receiver of claim 4 wherein the inhibit means further comprises a temperature compensating circuit for maintaining the response of the inhibit means to the pre-determined automatic gain control level over a temperature range.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US05/670,217 US4053843A (en) | 1976-03-25 | 1976-03-25 | Blanker inhibit circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1076651A true CA1076651A (en) | 1980-04-29 |
Family
ID=24689490
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA271,698A Expired CA1076651A (en) | 1976-03-25 | 1977-02-14 | Blanker inhibit circuit |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US4053843A (en) |
| JP (1) | JPS52117507A (en) |
| BR (1) | BR7701801A (en) |
| CA (1) | CA1076651A (en) |
| DE (1) | DE2713025B2 (en) |
| GB (1) | GB1525897A (en) |
| HK (1) | HK73979A (en) |
| IT (1) | IT1073174B (en) |
| MX (1) | MX143233A (en) |
| MY (1) | MY8000154A (en) |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS54111208A (en) * | 1978-02-21 | 1979-08-31 | Clarion Co Ltd | Noise elimination circuit |
| DE2929679C2 (en) * | 1979-07-21 | 1982-06-09 | Blaupunkt-Werke Gmbh, 3200 Hildesheim | FM receiver |
| JPS57196631A (en) * | 1981-05-28 | 1982-12-02 | Sanyo Electric Co Ltd | Detecting circuit for pulse noise |
| DE3227129A1 (en) * | 1981-07-20 | 1983-02-03 | Nissan Motor Co., Ltd., Yokohama, Kanagawa | Motor vehicle broadcast receiver with an RF interference suppression circuit |
| US4584714A (en) * | 1982-02-02 | 1986-04-22 | Nissan Motor Company, Limited | Automotive radio receiver with radio frequency interference elimination circuit |
| DE3233594A1 (en) * | 1982-09-10 | 1984-03-15 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Squelch method and arrangement for common-frequency radio networks |
| US4510624A (en) * | 1983-09-22 | 1985-04-09 | Motorola, Inc. | Noise blanking arrangement to minimize blanker splatter |
| DE3509968A1 (en) * | 1985-03-20 | 1986-09-25 | Haverkamp, Henrik, 6101 Bickenbach | Automatic noise gating device for audio-frequency signals |
| US4637066A (en) * | 1985-07-02 | 1987-01-13 | General Motors Corporation | Noise blanking signal generator for AM radio |
| JP5059677B2 (en) * | 2008-04-18 | 2012-10-24 | ルネサスエレクトロニクス株式会社 | Noise removing apparatus and noise removing method |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3140445A (en) * | 1962-08-03 | 1964-07-07 | Gen Electric | Communication receiver with noise blanking |
| US3299296A (en) * | 1964-11-12 | 1967-01-17 | Collins Radio Co | Low level threshold detector with temperature compensation |
| US3450834A (en) * | 1966-03-04 | 1969-06-17 | Sylvania Electric Prod | Automatic gain control circuit |
| US3613012A (en) * | 1969-10-13 | 1971-10-12 | Tracor | Adaptive blanking apparatus |
| US3725674A (en) * | 1971-07-08 | 1973-04-03 | Motorola Inc | Impulse noise blanker including broadband level sensing |
| US3699457A (en) * | 1971-08-11 | 1972-10-17 | Motorola Inc | Noise blanker circuit including rate bias and rate shutoff circuitry and audio blanking |
-
1976
- 1976-03-25 US US05/670,217 patent/US4053843A/en not_active Expired - Lifetime
-
1977
- 1977-02-14 CA CA271,698A patent/CA1076651A/en not_active Expired
- 1977-02-14 GB GB6088/77A patent/GB1525897A/en not_active Expired
- 1977-02-23 IT IT48185/77A patent/IT1073174B/en active
- 1977-03-23 JP JP3119377A patent/JPS52117507A/en active Pending
- 1977-03-24 BR BR7701801A patent/BR7701801A/en unknown
- 1977-03-24 DE DE2713025A patent/DE2713025B2/en not_active Withdrawn
- 1977-03-25 MX MX168515A patent/MX143233A/en unknown
-
1979
- 1979-10-18 HK HK739/79A patent/HK73979A/en unknown
-
1980
- 1980-12-30 MY MY154/80A patent/MY8000154A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| MY8000154A (en) | 1980-12-31 |
| BR7701801A (en) | 1978-01-24 |
| HK73979A (en) | 1979-10-26 |
| JPS52117507A (en) | 1977-10-03 |
| IT1073174B (en) | 1985-04-13 |
| DE2713025B2 (en) | 1978-08-10 |
| US4053843A (en) | 1977-10-11 |
| MX143233A (en) | 1981-04-03 |
| GB1525897A (en) | 1978-09-20 |
| DE2713025A1 (en) | 1977-09-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |