DD233784A1 - CIRCUIT ARRANGEMENT FOR GENERATING CLICK PULSES - Google Patents

Abstract

Circuit arrangement for generating click pulses. The invention relates to an electronic circuit arrangement for the objective Hoerpruefung, for generating rectangular pulses, which cause a so-called click in Hoerer. The aim is to provide such a circuit arrangement with which the pulse generation in a large control range is possible by less effort. The task is to make the regulation of the output level with remote control for the right and left ear and digital signals within wide limits adjustable. According to the invention, it is achieved by a circuit which has an OPV which is connected as a controllable constant-voltage source and whose reference voltage can be changed by means of different voltage dividers which can be connected by means of a decoder. Furthermore, the output circuit of the OPV is the operating voltage source of two switching stages, which are alternately controlled by a Verknuepfungsschaltung and in whose emitter circuits each have a headphone side. The circuit is applicable in electro diagnostics.

Description

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Vusführungsbeispiel

) The invention will be explained in more detail below with reference to an embodiment and a drawing. ;

η of the drawing shows: \

^: ig.1: a block diagram. ·

-ig. 2: a circuit diagram. | FIG. 1 shows the block diagram of a click-generating circuit. The core is a voltage-controlled voltage source 1. It generates the operating voltage for two switching stages 2 and 3. In the output circuit of the switching stages are

headphones 4. Switching right / left is done by means of an electronic switch 5. To mask the j

light-stimulated ear, a noise voltage source on one side of a headphone 4 via a relay contact 6 j

be switched. The reference voltages at the input of the voltage-controlled voltage source 1 are divided by several; Voltage divider, indicated by a resistor 7 and an adjustable resistor 8, provided. Which one

Voltage divider is effective, is decided by a decoder 9. Depending on the input data value at its digital input

the corresponding voltage divider is switched to ground. Due to the voltage divider ratio, the '

Output voltage of the voltage source 1 determines and thus the voltage, the pulse through the switching stages 2 and 3 ^; gets to the headphones 4. So it is only a variable operating voltage connected to the headphones 4, the

is independent in magnitude of a stimulus pulse generated by a pulse generator 10. The control of!

electronic switch 5 takes place by means of TTL signals "right" and "left", of an i, not shown in the figure

Calculator or control part to be delivered. The decoder contains binary coded signals for setting the volume, also j

in TTL level, on. j

2, the detailed circuit is shown. The voltage-controlled voltage source is output from the operational amplifier i

11, a transistor 12 and a resistor 13,14 and 15 are formed. It is a constant voltage source, but with the |

Reference voltage is changed. The output voltage at the emitter of the transistor 12 results in!

^U OFF -> .f <1 * Β-)

At the input of a NAND gate 16 and 17, the stimulus pulse is a rectangular pulse from a computer, not shown.

The signal "Right" / "Left" decides which switching stage is activated. For this it is necessary that the "right" / "left" signal is negated once. This is done with negator 18. If the "right" / "left" signal is high, the NAND gate 16 is opened, at low level, the NAND gate 17. The NAND gates 16 and 17 have open -Kollektor outputs. This is followed by the two switching stages 2 and 3, consisting of resistors 19,20, transistors 21,22, resistors 23,24 and transistors 25 and 26 at. The mode of action will be explained on a branch. The transistor 22 is a collector stage whose emitter resistance is formed by the coil of one side of the headphone 4. The resistor 9 provides the base current for the transistor 22,

when the transistor 21 is disabled. If the transistor 21 is open, the transistor 22 blocks. The transistor 21 is driven by the NAND gate 16. If the "right" / "left" signal is "low" at the input of the NAND gate 16, where the transistor 21 is opened. "High" level locks each "low-high" pulse at the stimulus input the transistor 21 and the transistor 22 opens for the duration of the pulse.

The voltage on the coil of one side of the headphone 4 is determined by the voltage at the collector of the transistor 22.

Changing this voltage will adjust the volume. The adjustment of the volume and the operation of the switching stage 3 for the other coil of the headphone 4 is analogous.

The provision of the reference voltage is effected by voltage divider, indicated by the resistors 27,28 and 29. The decoder 9 sets depending on the input data the associated voltage divider to ground. For mutual decoupling diodes 30 and 31 are connected in the outputs. By the variable resistors 28 and 29, the levels can be set exactly on the headphone pages. The resistor 32 indicates how the forward voltages of the diodes 30, 31, which limit the reference voltage, are compensated by a negative auxiliary voltage.

The connection of the smoke voltage, by a smoke voltage source not shown in the figure, is done with the relay contacts 6 of a relay 33. For switching, a transistor 34 is provided, which is controlled by the "right" 7 "left" signal, wherein a resistor 35 used for base current limiting.

Claims (2)

-1- 724 96 Claim: Circuit arrangement for generating click pulses for a brainstem audiometer, in which a voltage adjustable by digital signals within wide limits as a click pulse to an electroacoustic transducer, in particular a headphone and a stimulus pulse of defined pulse duration in the range of about 50th ..100 / XS is generated by a pulse generator, characterized in that there is provided as a controllable constant voltage source connected operational amplifier (11) whose reference voltage input to a plurality of different sized or set voltage dividers (7; 8; 27; 28; 19) is in communication and a decoder (9) is provided, at the inputs of which lies the binary coded output voltage value and at whose outputs the voltage dividers (7; 8; 27; 28; 29) are connected via decoupling diodes (30; 31) and the output of the operational amplifier (11 ) As an operating voltage source to two switching stages (2, 3) is set, the Aus each with a headphone side (4) are connected and the switching stages (2; 3) each consisting of a control transistor (21; 25) and a respective switching transistor (22; 26) and each switching transistor (22; 26) each having a NAND gate (16; 17) is connected, at their inputs on the one hand the stimulus pulse and on the other hand, the switching signal or the negated switching signal for the selection of a respective headphone side (4) is present. For this 2 pages drawings Field of application of the invention The invention relates to an electronic circuit arrangement for a brainstem audiometer with which an objective hearing test is possible. The generation of rectangular pulses in a large level range is necessary, which result in a so-called acoustic click in an electroacoustic transducer. Characteristic of the known technical solutions A click generator generates rectangular pulses, eg. B. with a pulse duration of 100 / zs, which are supplied to test each of the human hearing on one side of a headphone. At the same time, the derivation of brain stem potentials, whereby the electrical response of the brain can be determined. For an objective evaluation of the hearing, the rectangular pulses must be reproducible in a volume range corresponding to the audible range. The range is 0 ... 10OdB and can not be overstretched with an amplifier. It is known to provide such amplifiers on the output side with attenuators. These in turn require mechanical contacts in the form of mechanical switches or relays, which are known to be quite prone to failure. In addition, it is also important that mechanical switches are difficult to control remotely and relays have a relatively high power consumption. In the arrangement of control plates in front of the switches right / left and the output stages there is the problem that they have to process very small to very large levels. When switching small square-wave signals with relays, problems with contact reliability and contact resistance occur. With attenuators, a large number of resistors with non-standard resistance values, high load capacity and thus large space requirements are required. In addition, the spatial arrangement is difficult due to the necessary capacitive decoupling. In this design, the switching contacts must switch tiny signal voltages but also large currents, in another type very small and very high voltages. The disadvantages of these types are obvious. Since the stimulation for the derivation of brain stem potentials use square-wave pulses, only analogue working stages can be used in the arrangement of the controller before the switches right / left and the power amplifiers. There is also known a click generator for a brainstem audiometer whose output level is changeable in coarse and fine steps, the coarse steps being adjustable by switches and the fine steps by digital signals in conventional technology. This has a device for detecting a start pulse, a downstream driver, consisting of a switching part and a monostable multivibrator for reshaping the start pulse. The latter reaches a downstream amplifier, followed by the attenuator for coarse steps. The fine grading is done in the driver by means of the switching part. In the switching part z. As a frequency generator with subsequent parallel monostable multivibrators or frequency dividers, which are activated by AND circuits. The rule is to put together the total impulse, which ultimately causes the acoustic click in the headphones, from a variety of variable partial pulses, which are integrated by the inertia of the mechanical electro-acoustic transformation system into a single acoustic pulse. The sound pressure is on the one hand dependent on the pulse duration of the individual pulses in the fine tuning and on the other hand on the pulse height of the individual pulses in the connection of damping resistors in the coarse stage. In this embodiment, the high electronic complexity of disadvantage. Object of the invention This is to provide a circuit arrangement for generating click pulses, which allows the setting of an output level in a ^rvi large area with less effort on electronic or mechanical components. Explanation of the essence of the invention The invention is based on the reasons to establish a circuit arrangement to create more output level for the stimulation of the brain stem potentials by the delivery of acoustic click pulses to the right or left ear by remote control and digital signals within wide limits.
The object is achieved according to the invention according to the features specified in the claims.