GB1104713A - Improvements in or relating to noise blocking circuits - Google Patents
Improvements in or relating to noise blocking circuitsInfo
- Publication number
- GB1104713A GB1104713A GB2154665A GB2154665A GB1104713A GB 1104713 A GB1104713 A GB 1104713A GB 2154665 A GB2154665 A GB 2154665A GB 2154665 A GB2154665 A GB 2154665A GB 1104713 A GB1104713 A GB 1104713A
- Authority
- GB
- United Kingdom
- Prior art keywords
- circuit
- muting
- resistor
- intermediate frequency
- control
- 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
- 230000000903 blocking effect Effects 0.000 title 1
- 230000010355 oscillation Effects 0.000 abstract 2
- 239000003990 capacitor Substances 0.000 abstract 1
- 238000013016 damping Methods 0.000 abstract 1
- 230000004048 modification Effects 0.000 abstract 1
- 238000012986 modification Methods 0.000 abstract 1
- 230000002028 premature Effects 0.000 abstract 1
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers
- 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
- H03G3/341—Muting when no signals or only weak signals are present
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G3/00—Gain control in amplifiers or frequency changers
- 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
Landscapes
- Noise Elimination (AREA)
- Control Of Amplification And Gain Control (AREA)
Abstract
1,104,713. Transistor muting circuits. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. 21 May, 1965 [21 May, 1964; 4 Nov., 1964], No. 21546/65. Heading H3T. In a frequency-modulation receiver the limiter is arranged to be self-oscillatory in the absence of a signal and produce a control voltage used for muting. As applied to an F.M./A.M. receiver, with switch AM-FM in the F.M. position the A.M. intermediate frequency circuits AM I, AM II are back-coupled over capacitors C1, C2 so that the limiter T1 oscillates at the A.M. intermediate frequency when not biased back by a signal. The oscillations are rectified by the A.M. detector D1 and applied over resistor R4 to control a D.C. amplifier T2 whose collector circuit comprises a diode D2 forming a variable shunt across the discriminator circuit FM II: the switch-off level may be varied by means of resistor R5. A control voltage may also be taken off across resistor R1 and used to control the gain of an I.F. stage, or for other purposes, e.g. in a radio microphone it may be used for switching on a sound tape recorder. In a second embodiment (Fig. 3, not shown) the oscillations at A.M. intermediate frequency are applied to the centre of the F.M. discriminator circuit, so causing high conduction in the diodes which thus provide heavy damping on the circuit. In a modification (Fig. 4, not shown) the A.M. diode detector is biased conductive on F.M. and so damps the circuit AM II when momentarily low signal levels occur, preventing premature muting at such moments.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE1964T0026231 DE1257892B (en) | 1964-05-21 | 1964-05-21 | Device for generating a switching voltage dependent on the input signal in an FM receiver, in particular a squelch |
| DET27361A DE1273613B (en) | 1964-05-21 | 1964-11-04 | Device for generating a switching voltage for a squelch in an FM receiver |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB1104713A true GB1104713A (en) | 1968-02-28 |
Family
ID=25999880
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB2154665A Expired GB1104713A (en) | 1964-05-21 | 1965-05-21 | Improvements in or relating to noise blocking circuits |
Country Status (2)
| Country | Link |
|---|---|
| DE (1) | DE1273613B (en) |
| GB (1) | GB1104713A (en) |
-
1964
- 1964-11-04 DE DET27361A patent/DE1273613B/en active Pending
-
1965
- 1965-05-21 GB GB2154665A patent/GB1104713A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| DE1273613B (en) | 1968-07-25 |
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