Abstract: Conversion of an RF signal amplifier from an unbalanced signal configuration to a balanced signal configuration is provided while including an image trap for both sides of the balanced circuit. The grounded side of the secondary of a double tuned circuit is lifted from ground to provide a balanced circuit configuration. A trap filter is provided in the balanced circuit configuration by a pair of small capacitors coupled between the balanced secondary leads to appropriate signal nodes.

Abstract: A circuit configuration, especially in a television set, for range switching in tuners having at least two ranges includes at least two preselector stages each being assigned a respective tuner range. Each of the preselector stages is connected between a supply potential terminal and a reference potential terminal. Each of the preselector stages has an input terminal, an output terminal and an MOS tetrode. A switchgear for activating each of the MOS tetrodes has a switch output terminal being connected to the preselector stages and being connectable to the reference potential terminal. The preselector stages are coupled to one another for activating one of the preselector stages as a function of a switch state of the switch output terminal.

Abstract: A circuit configuration for range switching in tuners having at least two ranges includes at least two preselector stages each being assigned to a respective tuner range. Each of the preselector stages is connected between a supply potential terminal and a reference potential terminal. Each of the preselector stages has an input terminal, an output terminal and an MOS tetrode with a source terminal. A switchgear has switch outputs to be connected to the reference potential terminal for activating each of the MOS tetrodes. At least one resistor is connected between the source terminal of at least one of the MOS tetrodes and at least one of the switch outputs.

Abstract: An integrated tunable resonator (100) includes a common semiconductor carrier (110). Formed on the common semiconductor carrier (110) is an integrated voltage variable capacitor (104). A bulk acoustic wave resonator is formed on the common semiconductor carrier (110) and coupled to the voltage variable capacitor (104). In one aspect of the present invention, a thin film resonator (106) is coupled to the voltage variable capacitor (104) both of which are formed on a common semiconductor substrate (110). The combination of these three elements provide for a tunable integrated resonator (100). In another aspect of the present invention, a surface acoustic wave resonator (522), formed on a common semiconductor carrier (514), is coupled to a voltage variable capacitor (520) in order to provide a tunable resonator (500).

Abstract: A bandpass filter circuit arrangement in which a pair of parallel-resonant circuits (1, 2) are reactively intercoupled has a pair of signal input terminals (16, 17) connected to one of the resonant circuits (1) and a pair of output terminals (18, 19) connected to the other resonant circuit (2). Tuning of the filter is accomplished by varying the capacitive component of each circuit by varying the output of a tuning voltage source (20). In order to compensate for the deviation from the optimum intercoupling which would otherwise occur with change of tuning frequency the capacitive component of each resonant circuit is formed by two pairs (5, 7 and 6,8, or 9,11 and 10, 12) of capacitors in series, each series-connected pair effectively forming a varaible capacitive voltage divider to the tap on which the reactive intercoupling means (15) is connected. One capacitor (5, 6, 9 or 10) of each pair is variable, and all these are adjusted at the same rate.

Abstract: An amplifier loaded with a constant bandwidth tuned circuit is provided with an output series coil, and with a resistance in series with the output coil and a subsequent load to provide attenuation at high frequencies for maintaining the total overall gain of the amplifier and tuned circuit load constant with increasing frequency while simultaneously maintaining the bandwidth of the tuned circuit constant with increasing frequency.

Abstract: In a tuner circuit in which a plurality of band signals are received by a single common high frequency amplifier stage, a band switching circuit switches a resonant circuit to .lambda./2 type when the amplifier stage receives the highest band signals and to .lambda./4 type when the amplifier stage receives band signals other than the highest band signals.

Abstract: An RF signal input circuit for a UHF tuner of a television receiver comprises a series-tuned circuit including a varactor diode and an inductance element connected in series, in the order named, between signal ground and a gate electrode of a field-effect transistor RF amplifier. The series-tuned circuit has a relatively uniform bandwidth throughout the UHF range. A capacitor connected in shunt with the gate electrode completes a "split-capacitor" configuration in which the varactor diode and the shunt capacitor form a variable impedance transformation network for making the relationship between the effective impedances of the series-tuned circuit and FET amplifier relatively uniform throughout the UHF range. The order of the varactor diode and inductance element allows a low cost adjustable capacitor comprising a grounded shield wall as one plate and a movable tab as a second plate to be connected directly across the varactor diode.

Abstract: A mixer for mixing first and second signals for providing a difference signal comprises a mixing transistor. The first and second signals are applied between the base and emitter electrodes of the transistor. A non-linear impedance is coupled in series with the emitter electrode. Spurious signal components are reduced in amplitude compared with the difference signal.

Abstract: In an electronic tuning circuit for AM receiver including a radio-frequency tuning circuit and local oscillator circuit each using a variable capacitance diode, the local oscillator circuit comprises an oscillation coil; a padding capacitor connected in series with the oscillation coil; a first variable capacitance diode connected at one end in series with the oscillation coil; a first and a second fixed capacitor connected at one end in series with each other; and a second variable capacitance diode connected in parallel with the second fixed capacitor. The second fixed capacitor has its other end connected to a connection point between the padding capacitor and the first variable capacitance diode. The first fixed capacitor has its other end connected to the connection point between the oscillation coil and one end of the first variable capacitance diode. A tuning voltage is applied to the first and second variable capacitance diodes, thereby reducing tracking error over the entire receiving frequency band.

Abstract: A television tuner for three different frequency ranges comprises a common antenna connection for three input filter circuits (1, 2, 3). In order to obtain a simple circuit design which involves negligible mutual capacitive loads from the input filter circuits (1, 2, 3), the antenna connection (4) is spatially associated with the input filter circuit (3) for the highest frequency range and is directly connected to one end of a coupling conductor (5). The coupling conductor (5) is series-connected directly with the connection for input filter circuit (1) of the lowest frequency range I and, via a switching diode (11), with the input filter circuit (2) for the medium frequency range II. A further switch (12) detunes the input filter circuit (3) for the highest frequency range III if one of the other input filter circuits (1, 2) is activated.

Abstract: A receiver equipped with an electronic tuning circuit which uses voltage-variable reactance elements such as variable-capacitance diodes or the like in the radio-frequency tuning circuit and oscillation tuning circuit thereof. The oscillation tuning circuit includes a novel padding capacitor constituted by a composite circuit of a variable-capacitance diode and fixed capacitors connected at the position where a conventional padding capacitor is connected. With such an arrangement, it is possible to make tracking error negligibly small over a frequency band ranging from a low receiving frequency to a high receiving frequency, by applying a tuning voltage to the composite padding capacitor.

Abstract: In a tuner circuit, the relatively high voltage used to control a varactor diode of the circuit is derived using a cascade of resistors and transistors under the control of a reference voltage input. The breakdown voltage of each transistor is significantly less than the output voltage of the cascade and is such that the cascade can be implimented in the same semiconductor chip as high frequency, low voltage process, synthesiser components.

Abstract: A double-tuned circuit is provided of the type comprising a primary tuning circuit including first and second resonance coils connected in series and a first switching diode interposed between the connection point of the first and second resonance coils and the ground, and a secondary tuning circuit including third and fourth resonance coils connected in series and inductive-coupled with the first and second resonance coils, respectively, and a second switching diode interposed between the connection point of the third and fourth resonance coils and the ground, wherein band switching is preformed by turning on/off both the first and second switching diodes, which is characterized in that a bias voltage for turning on the first and second switching diodes is supplied to one of the switching diodes and through a conductive wire inductive-coupled with a sintered magnetic material to the other of the switching diodes, whereby an enlargement of the bandwidth and degradation of the flatness of the passband characte

Abstract: The invention relates to a variable capacitance element operating in the ultra-high frequency range. In order to integrate this element on to an integrated circuit chip, the element is designed so that the control voltage does not interfere with the ultra-high frequency signal and has neither filters nor shock chokes which are not integrable. The element according to the invention utilizes the junction capacitances variation of at least one diode, reverse-biased by a voltage across a resistor, the high frequency signal being at the diode anode. The element construction comprises an active zone in a semiinsulating substrate. Two metallizations partly cover the active zone and form therewith at least one diode. A projection to the active zone forms the resistor, to which is applied the control voltage. The diodes are p-n junctions of schottky diodes. The semiconductor material is Si or from the III-V group. Application to oscillators, filters, phase shifters, etc. in ultra-high frequency equipment.

Abstract: A variable capacitance circuit includes a varactor having an anode side and a cathode side. A first variable bias voltage is applied to one of the sides and one of a plurality of voltages is applied as a second bias voltage to the other side for controlling the capacitance of the varactor. A voltage multiplier circuit connected to a voltage divider network is used for supplying the plurality of voltages. A decoder is responsive to input signals for selecting and applying one of the multiple voltage outputs. The variable capacitance circuit is used in a voltage controlled oscillator of a frequency synthesizer for providing extended frequency range.

Abstract: A tuner in which a band switching signal corresponding to a channel selected from a plurality of UHF and VHF bands is generated to enable the formation of a suitable resonant circuit for receiving television signals of the selected channel. It includes a varactor diode, a plurality of resonant coils and distribution constant lines which are each grounded at one end. Each of the coils and the line is provided for forming a resonant circuit for tuning one of the bands. A plurality of switching diodes are provided for connecting the other ends of the coils and the line selectively to the other end of the varactor diode. The tuner further includes a device for turning on and off the switching diodes selectively in response to the band switching signal.

Abstract: In a tuning circuit apparatus comprising first and second tuning circuits having their tuning frequencies varied in a ganged fashion; a composite varactor device provides first and second Varicap diodes formed on a common semiconductor substrate, with anodes of the first and second Varicap diodes being led out to respective independent terminals and cathodes of the Varicap diodes being led out to a common terminal, first and second tuning coils are connected at first ends thereof to the independent terminals associated with the first and second Varicap diodes, respectively, first and second by-pass capacitors are respectively connected between second ends of the first and second tuning coils and the common terminal of the composite varactor device, and a control voltage supplying source parallelly supplies a control voltage to the first and second Varicap diodes.

Abstract: In a variable capacitance tuning circuit for high-frequency signals, a first varactor diode is connected between either the receiving end or feeding end and ground, one end of a tuning coil is connected to the receiving end or feeding end, and a second varactor diode is connected between the other end of the tuning coil and ground.

Abstract: A television tuner has a tuned circuit at the input of an RF amplifier. The tuned circuit has a varactor tuned parallel circuit and an output series coil for good high frequency attenuation and constant bandwidth with changes in frequency. For good low frequency attenuation, an input series capacitance is provided comprising a pair of varactors. The varactor pair is oppositely poled to reduce frequency doubling of low frequency signals.

Abstract: A tuning system employs a specific resonant circuit which includes two electrodes confronting each other through a dielectric interposed therebetween. Each of the two electrodes has at least one bent portion to present a lumped-constant inductance and has a desired equivalent electrical length. The two electrodes respectively have common terminals located out of mutually confronting positions so that voltage signals induced by mutual inductance between the electrodes will be opposite in phase so as to thereby produce a parasitic distributed-constant capacitance. The two electrodes form a two-terminal circuit network having a first terminal disposed at a desired position on one of the two electrodes and the common terminals as a second terminal. The first terminal of the resonant circuit is connected to a feedback amplifier, an amplifier, or a mixer so as to form a tuning oscillator, a tuning amplifier or a mixer.

Abstract: A multiband local oscillator of a television tuner comprises a common collector transistor amplifier, a feedback circuit for conditioning the amplifier to oscillate in the wide range of frequencies for VHF broadcast and cable channels and a tuning circuit coupled to the base electrode of the transistor. Bandswitching signals are applied to switching diodes in the multiband tuning circuit to produce tuned circuit configurations for the various frequency bands. When one band is selected, the corresponding bandswitching signal is coupled to the switching diode associated with a lower band to turn it on as well as the switching diode for the selected band to inhibit out-of-band oscillators due to parasitic elements of the tuning circuit.

Abstract: A combination UHF-VHF tuner has a switching diode placed in series with a VHF high-range peaking coil so that the coil forms a parallel resonance peaking circuit when high-range VHF signals are received and the coil acts as a series impedance matching element when a UHF IF signal is coupled from a UHF mixer stage.

Abstract: An oscillation circuit includes as its principal components a Clapp capacitor and two feedback capacitors connected to each other and a resonance coil. A first series circuit including a first variable-capacitance diode and a first DC cutoff capacitor is connected in parallel with the resonance coil, while a second series circuit including a second variable-capacitance diode and a second DC cutoff capacitor is connected to a first diode such that a certain polarity terminal of the second variable-capacitance is faced against the same polarity terminal of the first diode. One end of the second DC cutoff capacitor in the second series circuit is connected to the one of the feedback capacitors. Furthermore, means is provided at the joint of the first variable-capacitance diode and the first DC cutoff capacitor for applying a DC voltage to enable the first and second variable-capacitance diodes.

Abstract: In a VHF tuner, feedback capacitance between the emitter of a local oscillating transistor and the ground in a local oscillator is changed at the low band receiving state and high band receiving state by controlling a switching diode connected in series to a capacitor for feedback capacitance and, a mixer is installed to mix the output of the local oscillator and high frequency input. For an improved mixer biasing circuit, the switching diode in series connection to the capacitor for feedback capacitance is connected to one terminal of a mixing FET in the mixer, and changing of the feedback capacitance in the local oscillator is accompanied by changing of working current of the mixing FET in the local oscillator.

Abstract: An oscillator circuit suitable for use in a local oscillator of a tuner of a television receiver set. A feedback circuit comprised of a feedback capacitor (17) is connected between a junction of a tuning diode (10) and a correcting capacitor (11) connected in series therewith and the emitter of an oscillation transistor (1). Oscillation voltage developing across the correcting capacitor is fedback to the emitter of the oscillation transistor through the feedback capacitor. When the tuning diode is conditioned to have a large capacitance value, a large oscillation voltage is fedback to the transistor through the feedback capacitor whereas when the tuning diode is conditioned to have a small capacitance value, a small oscillation voltage is fedback to the transistor through the feedback capacitor. The oscillator circuit continues to oscillate stably over a wide frequency range whenever the tuning diode changes from the small capacitance value to the large capacitance value or vice versa.

Abstract: A television tuner comprises a voltage controlled variable capacitance diode provided in common to the UHF band, the VHF high band and the VHF low band. A tuning voltage provided from a channel selecting apparatus is applied to the variable capacitance diode as a control voltage. A relation between the tuning voltage and the receiving frequencies is selected such that the tuning voltage of the high end channel (the maximum receivable frequency) of the UHF band is higher than the tuning voltages of the respective high end channels of the remaining bands and the tuning voltage of the low end channel (the minimum receivable frequency) of the VHF low band is lower than the tuning voltage of the respective low end channels of the remaining bands. The channel selecting apparatus is adapted to restrict the upper and lower limits of the tuning voltage, whereby the upper limit of the receivable frequency of the UHF band is restricted and the lower limit of the receivable frequency of the VHF low band is restricted.

Abstract: A voltage controlled capacitor is created by connecting a capacitance between the output of an amplifier whose gain is voltage controllable and an inverting input of the amplifier.

Abstract: Stray capacitance is reduced in a wideband tunable oscillator network by arranging the resonant circuit as one or more series circuit branches wherein a variable capacitance such as a varactor diode is interposed between two substantially identical inductors. In the disclosed VHF-UHF oscillator, the inductors are realized by TEM transmission lines of the stripline variety. The stripline is formed by a multilayer printed circuit board arrangement and two resonant circuit branches are interconnected in a manner that permits biasing of the varactor diodes without the use of blocking capacitors in the resonant circuit path.

Abstract: A broadcast receiver is provided for mounting on board a motor vehicle, whose control circuit is entirely electronic. The receiver comprises a case whose front face, accessible to the user, is free from unevennesses or appreciable projections and which presents an opaque appearance when the receiver is stopped. The front wall is formed by a plate made from a tinted transparent plastic material. It comprises four sensitive zones which are formed by metallizations on the rear face of the plate so as to form capacitive proximity sensor keys. The indication of the wave range is effected by selective illumination of zones comprising graduations and/or by means of a double seven-segment display.

Abstract: Disclosed is an electronic channel selector comprising a plurality of diodes in series with a plurality of crystals, each diode/crystal connection defining one channel of the ten channel crystal-controlled oscillator. Non-enabled diodes are maintained in a reverse bias condition, preventing the associated crystal from oscillating in the oscillation circuit. The diode corresponding to the selected channel is forward biased into conduction permitting the associated crystal to control the oscillator circuitry providing the desired frequency output. When the selected diode is forward biased and begins conducting current, it conducts current through a path which provides a tuning voltage which may advantageously be utilized in a transmitter exciter filter or receiver preselector. A binary switch is manually set for the desired channel and produces a binary coded output. A binary-to-decimal decoder provides a single enabling output which is determined by the binary code supplied from the binary switch.

Abstract: Spaced conductive strips are formed on a substrate. A first transmission line transformer is connected between the input and one end of the first strip. A second transmission line transformer is connected between the other end of the first strip and the output. The second strip is connected to ground. A shunt tuning circuit is connected between the strips. The circuit includes first and second MOS capacitors mounted on and connected to the grounded strip. An RF choke interconnects the other side of each capacitor. A varactor diode is mounted on and connected to the first capacitor. An etched spiral inductor connects the varactor and the first strip. A bias signal is applied to the junction between the choke and the second capacitor in order to tune the filter.

Abstract: A tuner used in a television receiver or the like, when one supply voltage is given as a band switching voltage from a one-circuit triple-contact switch to selectively switch a VHF low band, a VHF high-band or a UHF band, a second contact of the switch selected for setting the VHF high band is connected through a second switching diode to the node of a high-frequency grounding condenser and a first switching diode for switching a tuning coil at a VHF input tuning circuit, a third contact of the switch selected for setting the UHF band is connected to the above node through a third switching diode so as to turn on the first switching diode even when receiving the UHF band, thereby generating no harmonic wave of VHF signal from a VHF input circuit by the first switching diode and no noise in the picture and also performing the setting of other bands without hindrance.

Abstract: A control system for adjusting a physical value, e.g. the resonance frequency of an oscillator comprising a bank of keys to provide the physical value as a digital word A, a microprocessor to convert the word A to a digital word B, a D/A converter to convert the word B to a voltage to control an electronic adjusting component of the oscillator, e.g. a varactor diode, and a measuring device to measure the output of the oscillator and provide a digital word C for coupling to the microprocessor. The microprocessor compares the word B with the word C and provides a correcting digital word .DELTA.B which is added to the word B for application to the oscillator through the D/A converter. This process is continued until the word B is equal to the word C.

Abstract: A radio frequency (RF) amplifier including a resonant circuit having a peaked response is tunable in response to a tuning voltage to select RF carriers over a wide range of frequencies and includes an additional resonant circuit for improving its response at the low frequency end of that range. The additional resonant circuit has a peaked response tunable in response to the tuning voltage in tracking relationship to that of the first resonant circuit. The tracking relationship is desirably selected so that the additional resonant circuit does not become tuned to a frequency which is an integral sub-multiple of the frequency of a selected RF carrier.

Abstract: An electronic tuning block including a plurality of screw drive type variable resistors are juxtaposed parallel to one another obliquely on an insulating substrate, and holes for receiving pointers fitted to the screws of the variable resistors and holes for receiving rotary knobs fitted to the tips of the screw shaft are formed on the upper surface of a box-shaped insulating case which is fixed to the insulating substrate.

Abstract: To suppress a fluctuation in resonance frequency caused by an input signal voltage in a tunable circuit, a respective capacitor is connected to each of two variable capacitance diodes connected in series-opposition.

Abstract: In a television receiver, two tunable traps are incorporated between the RF input and the tuner to attenuate undesired signals symmetrically located in frequency below and above respective desired RF carriers. The tunable traps are responsive to a control voltage generated independently of the tuning voltage for controlling the tuned circuits of the tuner so that the attenuation frequencies of the traps can be moved with respect to the respective frequencies of desired RF carriers to optimize interference reduction.

Abstract: An oscillator is described for use in the tuner of a television receiver which is tuned to a selected channel by a variable tuning voltage. The oscillator provides a higher than conventional power output at relatively low channel numbers by virtue of circuitry which changes the oscillator's operating current in response to the tuning voltage reaching a predetermined value. That predetermined value is selected to correspond to a relatively low channel number at which the power output of a conventional oscillator begins to decline.

Abstract: A circuit is provided for frequency drift compensation of a tuning diode in tunable RF-circuits, and comprises a temperature-responsive voltage divider coupled between an independent voltage supply source and a reference potential, the tuning diode being coupled to a tap of the voltage divider. In this circuit the separate tuning voltage source is not loaded down and may thus produce a tuning voltage which is independent of the variation of the voltage from the temperature compensation portion of the circuit.

Abstract: A key assembly for receivers for communication systems, especially radio television receivers, comprises a casing, keys adapted for mutual release by means of a spring-loaded locking plate for switching in storable, selectively adjustable electrical values of channel memories consisting of a plurality of voltage dividers for variable capacitance diode tuning, rotary and slidable press buttons associated with the respective keys for channel tuning and optionally for selecting a frequency range, which is adjustable in a preferably pressed position of the rotary press button being different from the tuning position by turning into various locking angular positions, as well as a channel and frequency range indicator scale. According to the invention said indicator scale simultaneously is the locking plate for the keys.

Abstract: A tuning voltage generating apparatus of a voltage synthesizer type comprises a voltage converter which converts into a reference voltage a voltage level of an input pulse signal having a pulse width corresponding to a frequency to be received and a low-pass filter which converts the pulse signal voltage converted by the voltage converter into a direct current voltage which is withdrawn as a tuning voltage. A reference voltage applied to the voltage converter is generated by dividing a voltage stabilized by a constant voltage diode using a resistor. A resistor voltage divider circuit determines the upper limit of the tuning voltage obtained from the low-pass filter. Two kinds of reference voltages having different levels may be generated as a reference voltage and switched associated with band switching.

Abstract: A printed circuit board lamination consisting of upper and lower printed circuit boards is provided with an area consisting of the sole lower printed circuit board, and a varactor diode and a resonance rod portion parallel to the lamination are arranged in this area. Thus, the length of lead of the varactor diode is reduced in effect, and also the effects of variation of the dielectric constant of the printed circuit board due to changes of the temperature thereof and relative humidity are reduced.

Abstract: A station selecting device which comprises: a plurality of variable resistors, grouped into several reception bands, the variable resistors in each group being connected in parallel; band selection switches for selectively supplying power to the variable resistors of the desired band; and channel selection switches for picking up the tuning voltage across the selected variable resistor, said each channel selection switch being connected to one of variable resistors of each band. Since each channel selection switch is connected to the variable resistor of each band, the number of the channel selection switches required are very few as compared with the conventional device, which in turn reduces the size of the device and makes the construction simple.

Abstract: Tuning circuitry for a VHF television (TV) antenna tunes such antenna for signals corresponding to the TV channel selected and couples those signals to the tuning system of a television receiver. An antenna has a pair of signal terminals across which the tuning circuitry connects to form a resonance circuit therewith for tuning the antenna. A variable capacitance responds to a control voltage to develop the appropriate value of tuning capacitance. Impedances, e.g. inductors or capacitors or resistors, are coupled to the resonance circuit at least at selected times by switches. An amplifier couples signals from the resonance circuit to the tuning system of the TV receiver.

Abstract: An electronic tuner capable of selectively receiving the UHF band and high and low channels in the VHF band is described which has a suitable resistance provided across power supply terminals in order to improve the separation between the VHF mode and the UHF mode.

Abstract: A conventional varactor tuned VHF/UHF television tuner with additional inductors placed in parallel in each VHF tuned circuit by means of diode switching provides an additional tuning capability over the CATV Superband. Selective tuning to any broadcast channel within the VHF, UHF and CATV bands is achieved by voltage-controlled tunable circuitry such as the type employing varactor diodes responsive to an adjustable DC tuning voltage having unique levels assigned to the various desired channels. By providing an additional bandswitching input voltage to a conventional tuner, Superband coils are diode-switched in parallel with VHF tuned circuits permitting an expanded tuning frequency range. This parallel coil approach in achieving Superband coverage permits the utilization of spring-wound VHF-band and Superband coils to facilitate tuning circuit alignment and to eliminate the need for a discrete Superband tuner or a CATV converter.

Abstract: Disclosed is a UHF-VHF combination channel selector for use with varactor diode tuners in which varactor control voltage is provided by a plurality of tapered potentiometers covering the various tuning segments. Non-detent, continuous channel selection is provided by rotation of a single control shaft to which is coupled a potentiometer wiper assembly. A substantially linear tuner control angular displacement versus channel number displacement over both frequency bands is achieved by compensating for varactor tuner nonlinearity over the VHF-band with complementary VHF selector potentiometers while hyper abrupt junction varactor diode manufacturing tolerances are compensated for by normalization of the UHF selector by means of upper and lower band tapered potentiometers.

Abstract: A tuning control apparatus for a digital automatic scanning tuner or a digital preset tuner employing a voltage controlled variable capacitance diode as a tuning element, wherein a tuning state detecting circuit is provided for detecting a tuning state responsive to a first signal which assumes the high level when the actual tuning frequency of the tuner falls in a predetermined frequency range which is higher than the correct tuning frequency being received and a second signal which assumes the high level when the actual tuning frequency of the tuner falls in a predetermined frequency range which is lower than the correct tuning frequency being received, and when the tuner is to be tuned to the frequency of a given broadcasting signal a tuning voltage being applied to the voltage controlled variable capacitance diode is varied in the upward or the downward direction, whereby the lower end of the second signal or the upper end of the first signal is detected, whereupon the lower end of the first signal or the

Abstract: A tuning apparatus includes a dial plate marked with broadcast frequencies thereon, a guide shaft provided in parallel with the dial plate, a substrate having a resistive layer thereon, the resistive layer having varying resistance values distributed therealong which correspond to the broadcast frequencies on the dial plate, the resistive layer being supplied with a DC voltage at opposite ends thereof, a plurality of markers, each slidably disposed with respect to the dial plate to indicate a predetermined broadcast frequency, and each having a first engaging portion and a first electrically conductive slide element for slidably contacting the resistive layer to detect a predetermined DC voltage in response to the location of the markers, a mounting member slidably disposed on the guide shaft in parallel with the dial plate, and including a display member extending therefrom toward the dial plate to indicate a manually selected broadcast frequency, a second electrically conductive slide element for slidably c