Abstract: An electrodynamic loudspeaker having a cone diaphragm within which there is arranged a centrally located body which influences the acoustic radiation. This body is formed by an extension of the magnet core of the moving coil which extension is enlarged in the region of the mouth of the cone to form a partial covering of the cone chamber up to about half of the diameter of the cone mouth. The central part of the covering is approximately equal to one and a half times the diameter of the magnet core and forms a closed surface. In the remaining edge area of the covering there are axially arranged passages, the cross-sections of which occupy approximately one-half of this edge area.

Abstract: A switch device for a turntable with a starting device which closes the switch for the drive motor on the one hand by means of a swinging movement of the pick-up arm manually during swinging-in from its support bracket onto the record, and on the other hand by means of a direct current dc low voltage solenoid which is actuated by momentary actuation of an operating service element, the latter being connected with a first contact pair, and a switch-off device which acts automatically with the arriving of the pick-up or reproducing head in the run-out groove of the record, the switch-off device opening the switch for the drive motor and containing a switch for the entire current supply of the device from the power supply mains.

Abstract: A control device, actuatable by electric solenoids, for the drive unit of a tape recorder, in which the tape, in addition to the normal forward for recording and playback can also run fast forward or reverse, all three drive settings being obtainable with only two solenoids, which solenoids act on two opposite arm ends of a T-shaped lever which has a centrally located pivot bearing. The lever can also be translated in a cross direction and is pulled by a spring against abutments which are disposed opposite the solenoids, so that by suitable switching of the solenoids it can be rotated or even only translated. By the translation the normal forward speed can be set and upon rotation the fast forward or fast reverse can be set by the third arm of the lever.

Abstract: Transmission system for digital control of electrical devices, by means of standardized or uniformly releasable pulse combinations corresponding to the desired control operations, which pulse combinations are sent selectively at least from a first and a second of the devices to be controlled to a two-conductor line system, which line system connects all devices in parallel with each other, whereby the connection line is under a constant bias voltage.

Abstract: A switching device for a cassette tape recorder with which the magnetic head, by means of a feed device which is actuatable by a solenoid, is introducable into an opening of the cassette and is again removeable by means of a spring, whereby in the circuit of the solenoid there are disposed in series a first and a second electronic switch and a mechanically controlled first contact pair, and the first electronic switch is controlled by the service control elements for the tape transport (recording/playback or stop), the second electronic switch being controlled by a photoelectric device which is disposed in the region of grabbing of the fingers upon insertion or removal of the cassette and interrupts the circuit of the solenoid as long as the light beam is interrupted by the fingers and the first contact pair is controlled by a sensing pin which projects into the reception area of the cassette and interrupts the circuit of the solenoid as long as no cassette is located in the device, so that the magnetic head

Abstract: A method for production of a turntable which carries stroboscope marks with a metallic surface on the face side of its rim, the metallic surface relative to its dark colored intermediate spaces being elevated. In the edge vicinity of a disc which is made of good deformable metal and which by bending its edge downwardly forms the face side of the rim of the turntable, before the bending of the edge, recesses are stamped-in, which recesses correspond to the intermediate spaces of the stroboscope marks. After the bending and the dark coloring, the disc is lightly cut in the width of the stroboscope marks, which width is chosen somewhat smaller than that of the stamped-in intermediate spaces, in order to achieve a contrast in lightness between the lightly cut stroboscope marks and the deeper intermediate spaces. The turntable comprises a lower part substantially contributing to a flywheel mass, on which lower part there rests a disc as an upper plate, the disc being non-rotatable with respect to the lower part.

Abstract: A pick-up with a carrier element, on which a capsule which contains the electro-mechanical transducer is exchangeably fastened, in which capsule a needle carrier is held pushed-in up to an abutment, and an arm for handling the pick-up is pivotally mounted in the carrier element. A pin is mounted in the capsule substantially transversely to the push-in movement of the needle carrier. One end of the pin can be guided into a recess in the needle carrier and its other end is coupled with the arm such that the pin with said one end is able to be brought in or out of engagement with the recess of the needle carrier by pivoting the arm.

Abstract: A protective arrangement for a cassette tape recorder in which a magnetic head has a face side facing upwards, and is located within the recorder. A protective hood covers the face side of the magnetic head, and is rotatably located about a horizontal axis which is perpendicular to the gap plane of the magnetic head. A coiled spring engages the protective hood, and urges it into a closed position. A switch for connecting the recorder to a power supply line, is connected to the protective hood, by a connection located so that upon moving the switch to an ON position, the protective hood is moved to an open position against the action of the spring. When the switch is moved to an OFF position, the movement of the protective hood to its closed position is released. A stop located on the protective hood, enters behind the cassette placed in the recorder in the opening position of the protective hood.

Abstract: A tape recorder with a motor-containing-drive device for normal forward running (record or playback) and for fast rewinding of the recording tape, and a carrier plate on which the magnetic heads are arranged. The carrier plate is displaceable in its plane with the corresponding drive device of the tape by operating elements for setting of the operating modes "record" or "playback," whereby by the displacement of the carrier plate into its operating position, a switch, which sets the motor of the drive device in operation, is closed and by which the magnetic heads are brought into engagement on the recording tape. The operating elements for the fast rewinding are set for a displacement of the carrier plate however only over a portion of its displacement path. The switch for the motor current is coupled with the carrier plate such that it closes with the displacement of the carrier plate over this portion of its displacement path in the direction of the operating position of the carrier plate.

Abstract: A tape recorder in which a counter indicates the tape length traversed in the recorder. The counter may be returned to an initial position by a manually operated element. A switching unit for shutting off the drive for the tape, is coupled to the counter so that the drive for the tape is shut off when the counter has returned to its initial position. The counter, furthermore, may be set to a pre-initial position ahead of the first-mentioned initial position by an amount of tape length which corresponds at least to the length of a dead portion of the tape, on which no recording or playback is possible. The recorder is also provided for resetting the speed of the tape from normal speed for recording or playback, to fast speed in the forward and rewind directions. The shutting off of the drive may be operated so that it becomes ready to function only when the fast forward setting is made. The counter may have numbered dials mounted on a common axis and bearing the indicated numbers on their circumference.

Abstract: A drive device for a tape recorder by which the recording tape is drawn off one spool by means of a capstan, and is wound-up on another spool, which is driven over a friction coupling by a motor with a speed not substantially above the highest required winding speed, with a drive device driven by the same motor, the drive device for the purpose of fast rewinding being selectively coupleable on one of the two spools. The two drive gears are arranged on a swingable carrier arm driven continuously in oppsite working directions by a stationarily arranged motor via a belt. By swinging the carrier arm in opposite operating directions out of a neutral center position, the drive gears are coupleable from time to time with one of the spool-carrying winding spindles for fast rewinding.

Abstract: A stand which is assemblable by laymen for insertion of phono-devices, accessory units and sound carriers, which is able to be expanded starting from a base unit which corresponds to a so-called phonotable, by mounting thereon assembly elements, which respectively form a stand compartment.

Abstract: A circuit for connecting a loudspeaker combination having a treble loudspeaker to an amplifier with a control device for emphasizing the amplification in the range of the treble frequencies, comprising a positive temperature coefficient resistor connected in parallel to a fixed resistor. The parallel resistor combination is connected in series in the electrical connection means for the treble loudspeaker and substantially through the first-mentioned resistor has a value which during normal operation of the loudspeaker combination is smaller than that of the treble loudspeaker, and further has a temperature coefficient such that by exceeding of a permissible constant load voltage for the treble loudspeaker, its resistance value increases with respect to the treble loudspeaker such that the latter is not thermally overloaded. The fixed resistor limits the resistance increase of the resistor combination to a predetermined value.

Abstract: A magnetic tape recorder for recording as well as for playback of sound, having a noise suppression device, and sensor member with an abutment surface for engaging against an unopened break through tab of a tape cassette for causing a locking mode for the recording device to be inoperative. The sensor member has an additional abutment surface arranged such that the latter abutment surface senses the wall of the cassette outside of the broken-through penetration opening of the cassette and the insert movement of the sensor member is limited in the opened penetration opening. The sensor member is connected with the locking device; such that in the absence of the limitation due to the absence of a cassette, the locking device, is also inoperative.

Abstract: A record player drive, comprising a belt pulley concentrically disposed relative to and connected with a turntable, a motor having a motor shaft containing sections of different diameters, and a drive belt connecting the belt pulley with the motor shaft. A guide fork shifts the belt on the sections, and an operating element stepwise sets different turntable-rotational speeds. A holder keeps the operating element in positions corresponding to drive rotational speeds of the turntable, and an elastic coupling is disposed between the guide fork and the operating element for exerting a shifting force on the guide fork when the operating element is moved with blocked guide fork in another drive position. A switch opens and closes the motor electric circuit, and a blocking device blocks the shifting movement of the guide fork, and is coupled with the switch such that with opened electric circuit the blocking is operative and with closed electric circuit is inoperative.

Abstract: A pivot hinge for an apparatus cover hood comprising sleeves concentric to the pivot axis and axially displaceably yet non-rotatably arranged relative to the housing bottom part on the latter, and the face sides of the sleeves, respectively, being formed with curved courses. A cam is pivotally mounted about the pivot axis and with respect to the cover hood rotates therewith.