SE428986B - TONALSTRARKRETS - Google Patents

Description

10 15 20 25 30 8102406-9 The invention is described in more detail below with reference to attached drawing. Fig. 1 is a block diagram of an electronic tone generates and shows the most important functional circuit components 'in the tonal generator and their association with each other in accordance with the invention. Figs. 2 and 3 are a schematic schematic diagram showing the detailed circuit in an embodiment of the electronic the tone generator of the present invention. Fig. 4 illustrates this the relationship between Figs. 2 and 3. Fig. 5 shows a signal rator circuit according to another embodiment of the invention.

In one embodiment of the invention, there is a tonal to which power is supplied by using constant current for optimal operation in an area with a wide range of loop length and supply voltage levels. Use of transit constant current generators biased by fixed resistors and non-bypassed emitters, gives a fixed current value independently of the working voltage within a large working area. The current value is is matched by the base voltage and the emitter resistance. A high impedance up- enters the collector. Interconnection of two such generators, an NPN transistor and a PNP transistor, so that they are complementary arranged over a line facilitates operation of the sound generator circuit components with constant current and at the same time means that high dance appears on both sides of the circuit components.

The tone generator also comprises on the one hand sensing means for special distinction between valid ringtones and unwanted transients, oscillation generator means for activating an output signal converters via circuit means, and frequency determining means for variables ation of the frequency of the generator means and partly power conversion means for generating ringtone power from the incoming ringtone.

The structure of the circuit is such that its realization in the form of a integrated circuit can be done with a minimum number of external components.

The sensing means function to distinguish between valid and invalid ringtones by considering the duration of the ringtone above a certain, fixed voltage level. This effect is achieved by initiating 10 15 20 25 30 35 HO 3 8102406-9 comparison and then integration of the input voltage. During the interval when the input voltage exceeds a first reference voltage level, a capacitor is charged from a first power source. El- jest the capacitor is discharged by a second power source. About the input voltage caused by a valid ring signal, the capacitor will be charged to a voltage exceeding a second reference voltage level, at which time the tone generator and the converter are activated emits sound. If the input voltage is caused by a selector pulse or switching transient, the capacitor will not be charged to the sufficient for its voltage to exceed the second reference voltage level, which prevents the converter from sounding. Sålun- conventional ringtones will then be able to activate the tonal clean and cause an audible output signal, while transients and pulses up to levels of several hundred volts are incapable of doing so.

The generator means determine the frequency and the pulse ratio at the signal driving the converter. Power for the generator is obtained by means of constant current generators from the incoming ring signal.

Amplitude modulation of the signal fed to the converter takes place li- by means of the incoming ring signal. The generator means are seen with a resistor capacitor combination that sets the frequency of the generated signal, while the attw pulse rate is determined by the ratio between two of the constant current generators. Oscillators fundamental frequency can be changed by adjusting the resistor ~ or the capacitor values while maintaining the same pulse ratio.

In order to achieve distinct ringing ability in accordance with the invention, changes in a state of operation the fundamental frequency of the generator by means of frequency determining means. The fundamental frequency changes with a fractional ratio, such as the ratio 5/4, during the incoming ring signal lens negative half-period. This makes it possible to obtain a frequency shift type signal in addition to the amplitude modulated standard the signal. The pulse ratio remains unchanged during the generation of the frequency the shift signal.

The task of the power conversion body is to convert income ringing signals to the energy required to achieve of the reference voltage of the circuit and of the current generators and the power requirements of the converter. Power is applied to the converter separately from power is supplied to the power generators, which in turn supply the generating components with effect. This power separation for both purposes enable better control of the power generators and adequate amplitude modulation of the converter signal. '10 15 20 25 30. 35 H0 810240649 or 1 Pig. 1 shows a functional block diagram of a tone generator "W" working according to the principle of the invention. As can be seen from the figure goes in the tone generator power conversion means 200 connected to a pair incoming lines 101, 102, over which incoming ring signals received. The function of the conversion means 200 is to rectify it incoming ring signal and also serve as a power source for residual part of the tonal master circuit. This also includes voltage limitation circuits to limit the maximum voltage generated the rest of the circuit. In addition, the power conversion means 200 serves as a voltage source which drives the electroacoustic over line 103 converter 300. _ _ Sensing means 400 are connected across the output means of the conversion means 200. conduits 104 and 105. These bodies 400 determine the existing of a valid ringtone. Discrimination between valid ring signals and selector pulses or switching transients are determined by the input signal voltage remaining over a reference time for a longer period of time. purge voltage level. over the lines 104, 105 are also connected oscillation generators rator means 500, which generates the signal driving the circuit means 700.

The frequency at which the generator means 500 operates is controlled by the frequency determining means B00. During a work permit, the frequency band the tuning means that the generator means operate at a fundamental frequency, transmitted to the converter via the circuitry 700. During a second operating conditions cause the frequency determining means 500 to the generator means 500 emits a frequency-shifted output signal which the means 700 are transferred to the converter 300. In the output circuit means 700 includes a latch circuit which, when actuated by the sensing means 400 is switched on and off at a rate determined by the generator means S00. When the circuit means 700 are activated by both the sensing means H00 and the generating means. 500, they establish via the line 106 a current path from the the converter to the line 105.

Fig. 2 shows a detailed principle diagram for the tone generator circuit according to fig; 1. The incoming ring signal on lines 101, 102 is input to the power conversion means 200, namely to a diode bridge consisting of diodes 201-ZOU and also a diode 205. To the latter diode 205 is connected to an electroacoustic converter_300 and circuit organs 700, which will be discussed in more detail below. Diode bridge one output is connected to a diode 206, which in combination with a capacitor 207 transmits power to the tonal current circuit components.

The output of the diode bridge is also connected to a resistive voltage 10 15 '20 25 30 35 40 5 8102406-9 divider network consisting of resistors 208, 209, 210. An outlet, puncture of this voltage divider leads to a Darlington transmission resistors 211, 212, which supply a voltage regulator formed by transducer the transistors 213, 214, 215. The transistors 213 and 215 operate due to reverse direction breakthroughs at their base-emitter transitions as zener diodes. These transistors have several functions. Together with resistors 208, 209, 210 and transistors 211 and 212 they limit the maximum voltage at point 11 to a certain level.

This restriction provides a safe margin to the maximum allowed the voltage for it in the manufacture of the integrated tone generator circuit use conventional technology with embedded collector. For secondly, at point 12 they give a voltage which is used as an indication to the sensing means 400, see below. Finally provides transistor 215 is a voltage reference used to determine the current in all power sources in the tone generator circuit.

The voltage determined by transistor 215 at point 13 a current determined by resistors 216-220 and transistors 221, 222, 223 base-emitter voltage drops, the emitter of the transistor 221 current (minus the negligible base current of this transistor) constitutes transis-a tower 224 emitter current (excluding transistors 224 and 225 small base currents). Transistors 224: 225 and 226 and transistors The sensors 401, 402, 403 in the sensing means 400 thereby form a current mirror, where the emitter current of the transistor 224 is reflected or proportioned emitted in the emitters of the current mirror transistors in accordance with the punch value in the respective emitter line. Thus, the current is in the emitter leads of the transistors 226, 402 and 403 are twice as large as the emitter current of the transistor 224 because the respective emitters resistors 227, 404 and 405 amount to half of resistor 228 value, while the emitter current of the transistor 401 due to resistor 406 is twice the size of resistor 228 the current in the transistor 224. It should be noted that the number is uniform collectors for each transistor are indicated by the number of collectors leads. Transistor 225 is used as an auxiliary transistor for current the base drive of the mirror. Due to the fact that the transistor 226 has split collector with equal areas, each collector will - designated "a" and "b" - to carry half of the total emitter current. Vidarea the emitter current of the transistor 401 is divided into five different large parts by means of the five collectors, with three-fifths of the current being led to ground point and one - fifth to each of points 14 and 15. s1c24os-9. 6 10 15 20 25 30 35 UO In accordance with the instructions given by T.M. Frederiksen, W.M.

Howard and_D.M. Monticelli in the essay "A Single-Chip, All Bipolar, Camera Control IC "- presented at the 1977 IEEE International Solid State Circuits Conference, February 18, 1977, and reproduced in "ISSCC 'Digest of Technical Papers', pages 21H-215 - divided by transistor # 07 emitter current in five equal parts, four of which are shunted to ground the remaining part and the remaining part is fed to the transistor 408 collector. This transistor forms together with the transistors H09 and 410 an additional current mirror with the transistor H11 operating as auxiliary transistors. Transistor 412 is used to make transistors-i H1 and 413 base currents are equal in magnitude by passing through transistor 410 collector current compensates the base current of transistor 413. This current is carries a significant addition to the discharge current of capacitor 414 if the gain of the transistors were low. Transis- emitter currents 409, 410 and 412 have established values such as depends on the relative size of the emitter junctions (indicated by number of emitter conductors) and the values of the emitter resistors.

The collector b of the transistor # 01 is connected to the emitters of a differential coupled transistor pairs 415, 416, which form a comparator 'with one pair of transistors always on. When the transistor H16 is : nur ... uH-f .... ._ .. .... conductive, the current is conducted from transistornsßíO1 collector b to ground. .now On the other hand, when transistor H15 is conducting, four-fifths of the current is but from the collector b of the transistor 401 b to ground and one-fifth more point 16 for charging the capacitor 414.

The collector current of the transistor 22H is essentially the same as the emitter current of the transistor 223 (disregarding the base currents).

Transistor 223 forms a current mirror with transistor 417 in Fig. 2 = '. fl! -' ¥ - '? Y -': -. «.-.-.- e ..- .. v ._-.......» - .. and transistors 601, 502 and 503 in Fig. 3. Transistor 222 is used as an auxiliary transistor for this current mirror.

The function of the sensing means depends on the voltage level at the point 12 and on the voltage across capacitor 41U. As soon as clamping of sufficient size is supplied, transistor 215 begins to perform its control function and the power sources are activated. Transistor 215 holes f..n..1 .m ... m.x .._. ~ .- ..: .... \ read in the control state of the current in the collector a of the transistor 226 a.

Constant voltages are established along the resistance chain 216-219 :, ^. x.I! I.-l - ::. and these voltages are taken out as voltage references. Voltage the reference at point 17 is used in the generator means 500 as discussed later, while the voltage reference at the one with the transistor point 1818 connected to tower 418 establishes the minimum voltage densifier 41% is allowed to charge to. Point 19 provides one IN L_ fVIul-nh: ïlllm |: l | uh -: - !: Fr: 1 ..- l :: v-a-: h- 10 15 20 25 30 35 40 7 8102406-9 reference voltage for the base of the transistor H19. Transistor v19, iven riven via the resistor H20 of the current in the collector b of the transistor 226, supplied maintains a voltage at the base of transistor H15 when transistor 433 is strangled. Transistor H16 has its base connected to point 12, whose voltage is proportional to the full-wave rectified voltage.

As previously indicated, it controls the differential the transistor pair 415, H16 the charge of the capacitor H14. When tension the voltage at point 12 is lower than the reference voltage at the transistor 415 base, transistor 416 is conductive and transistor H15 is throttled, where at the current through the collector b of the transistor 401 flows to ground. Un- This time, capacitor 414 is discharged from the collector of transistor H10. Current. When the voltage at point 12 is higher than the voltage at However, the base of the system 415 is the transistor 415 conductive and the transistor tower 416, the current in the collector of transistor 415 being reduced by damage with the current of transistor 410 is used to charge the capacitor U1U. The voltage across capacitor 414 will rise according to one triangular waveform determined by the time during which the voltage in point 12 is greater than the voltage at the base of transistor 415. Through use of small charging and discharging currents can condense tower H14 be relatively small and inexpensive.

Transistors 409, # 13, 417 and Û21-42% form an amplifier with the gain one and acts as a buffer between the high-impedance diva point 16 and the lower impedance having the base of the transistor tower 425. Transistors 425 and 426 form a differential pair.

The base of transistor 426 is supplied with a reference voltage determined by sistorns H03 constant collector current, a voltage level change transistor H27, resistors 428, N29, 430 and 431 and the current in transistor 425.

When the voltage across capacitor 414 is lower than the voltage at the base of transistor # 26, transistor 425 is conductive and transistor 426, with the collector current of the transistor 402 via the transistor 425 and resistor # 30 floats to ground. This extra current through the the MÉG state raises the voltage at the base of the transistor H26 and provides more circuit hysteresis in the following way. When the 41U capacitor is charged enough to raise the voltage at the base of transistor 425 to approximately the same voltage as at the base of transistor H26, more transistors to turn on so that transistor 425 is throttled and transistor 426 becomes conductive. At this point, three things happen at the same time. First, three quarters of transistor 426 flows emitter current to the circuit means 700, which will be discussed later, so that : .- -g-n-v fi- n. run-u. www-uu ... 10 15 20 25 30 35 HO 8102406-9 «s these are activated and allow ringing to start, as the the rator means 500 at this time generates a signal. For it second, a quarter of the emitter current of transistor 426 flows to the collector and base of transistor 432, which together with transistor H33 forms a current mirror. The relationship between the issuer resistors H34 and H35 for transistors 432 and H33 is such, that the collector of the transistor H33 emits a current as subtracted from the current in the collector b of the transistor 225, leaves a low current through resistor 420. This current reduction serves to reduce the reference voltage at the base of transistor 415 to a level which is sets the tone generator to remain on once it is turned on started to sound. Such a reduction is necessary, since the converter the load - after the tuner has started working - causes that the incoming ring voltage falls below its positive half- periods. Finally, the liquid collection through the resistor 430 ceases. the current through the transistor 425, the reference voltage at the base of the transistor H26 is lowered to a level which ensures that the the generator remains on. After a valid ringtone has been identified locking will thus be ensured as a result of the reference level the shift. Selector pulses and other transient signals are not detected by these bodies because their levels and durations exceed the reference the voltage at the base of the transistor A15 is less than resp. shorter than that incoming ring voltage. Thus, the 41% capacitor is not charged sufficient for the reference voltage at point 30 to be exceeded; why ringing is absent at such signals.

Fig. 3 schematically shows the generator means 500 of the tone generator circuit, frequency determining means 600 and circuit means 700. Generator means 500 functions in a similar way to the sensing means H00 in this respect that charging and discharging a capacitor by means of complementary connected constant-current sources are used to set the frequency and heart rate ratio. In this case, a capacitor 505 responds to the charging and discharge current sources, which are constituted by the transistors 50% resp. 503. Depending on which of the differential pair transistors 506 or 507 which is conductive, capacitor 505 will either be charged or discharged. As previously indicated, transistors 501, 502 and 503 part of current mirrors formed by the transistor 223 shown in Fig. 2.

The collector currents of the transistors 502 and 503 are equal after all power sources are enabled. If transistor 510 is throttled, the reference voltage at point 17 (Fig. 2) minus the base of transistor 508 emitter voltage Vbe plus the voltage drop across the resistor'51U that 10 ¶5 20 25 15 NO 8102406-9 appear at the base of transistor 506. Initially, the capacitor is 505 is discharged, so that the base of the transistor SO than the base of transistor 506, which causes transistor 507 to be throttled and transistor 508 conductive. As a result, the transistor floats 502 collector current through the transistor 506 and becomes substantially trans sistor 509 emitter current. Transistor 509 here forms a current Mirror with transistors 602, 510, 504 and 511. Transistors 512 and 513 form a Darlington auxiliary transistor for delivering base current to the current mirror.

The current through the transistor 510 flows through the resistor 514 and transistor 501 to ground. The voltage drop across the resistor the state 51k is added to the emitter voltage of the transistor 508 and increases voltage level at the base of transistor 506. At the same time, the trans- collector current of the resistor 504, reduced by the collector current of the transistor 503 current, capacitor 505, and collector current of transistor 511 flows through the resistor 515 and opens the transistor 515. When the transistor tower 516 is conductive, the output transducer 701 is prevented from opening independent of the presence of collector current of the transistor H26. Condensed The sensor 505 continues to be charged by the transistors 503, which shot collector current until the charge reaches a voltage level equal with the level at the base of transistor 506. Shortly thereafter, the transistor becomes 506 base-emitter junction biased in the reverse direction due to it reduced the current through transistor 510, and transistor 507 the base-emitter junction is biased in the forward direction, thus transistor 507 turns on and transistor 506 turns off. The switching of these two transistors are promoted by the transistor 517 with split collector. At this time, the collector current of transistor 502 flows through transistor 507, and the current built up around transistor 509 the mirror turns off. The introduction of the resistor 518 improves this power mirror switch-off properties.

When transistors 507 and 506 change state, the transistor the base voltage of the sistor 506 that with the voltage drop across the resistor 514 lowered to the original reference voltage level. The capacitor 505 then begins to be discharged by the constant carbon of the transistor 503. senior lecturer. Furthermore, the base drive of the transistor 516 ceases, which therefore strangled. If a valid ringtone has been detected in accordance with as discussed above, transistor N26 will output current to the circuit means 700 so that - when the transistor 516 is throttled - the current in transistor H26 serves to drive the circuit means 700 transistor 701 to conduction state. In this way is thus achieved "s1o24oe-9 10. a ring frequency is shifted tiva half periods. The frequency determining means include transistors \ 601-604 and resistors 805-610. The possibility of frequency shifts is achieved in that the base of the transistor 604 via the resistor 610 and a switch such as the switch 611 is connected to the line 102 in Fig. 2. w 20 25 30 10 an inversion of the oscillator output voltage. Capacitor 505 then continues to be discharged via transistor 503 until then that its voltage has dropped to the voltage level at the transistor 506 bas. At this time, transistor 507 is throttled below it that the transistor 506 turns on again and supplies them around the transistor tower 509 mirrored the power sources. The base of the transistor 506 returns to its previous voltage level, capacitor 505 begins to charged and the oscillation is repeated. ' The frequency determining means 600 allows the possibility of an output signal of the frequency modulated type by oscillating the generator means 500 during the negative of the incoming ring voltage During the negative half periods of the input signal, the transistor 604 arrives to be biased in the forward direction so that base current is shunted away the transistor 601, which is hereby throttled, as well as the transistor 603. This mode of operation allows the transistor 602 to become part of the circuit sistor S09 formed the current mirror so that current can be shunted from the transistor S10 via the resistor 608 and the transistor 602 to ground.

The result is that lower voltage is generated at transistor 506 base, which in turn reduces the voltage at which The capacitor 505 must be charged to bring the transistors 506 and 507 to spare. This in turn reduces the capacitor 505 charging and discharging times and thus increases the frequency of the oscillator kvens. During the remaining negative input signal periods, the transistor comes on 602 to cause a decrease in the collector current of the transistor 510 and thus giving rise to the increased oscillation frequency. The value of the the position 608 is selected so that the increased frequency has the harmonic the ratio 5 / H to the frequency of origin and thus gives rise to a pleasant sound. It should be noted that the pulses of the two frequencies quotas remain the same because the charge and discharge capacitors of the capacitor 505 10 15 20 25 30 35 HO 8102406-9 11 current flows are unchanged. If the frequency shift option is not used, transistor 601 remains turned on and thus holds transistor 603 bottomed. As a result, the transistor remains 602, whereby no current is removed from the transistor 510 and the oscillator retains its original frequency.

The output means 700 for the tone generator is formed by transistors 701, 702 and a resistor 703 coupled in thyristor equivalent combination nation. When a valid ring signal is identified by the sensing means 400, as previously discussed, a continuous current will fed from the collector of the transistor 426 to the circuit means 700. Eph. since the generator means 500 are in operation at this time, transistor 516 will turn on and off in accordance with frequency and heart rate ratio of these organs. When transistor 516 is turned on turned on, the gate current from transistor 426 will pass its collector, so the thyristor equivalent will be throttled.

When the transistor 516 is turned off, the thyristor equivalent will be reversed be conductive due to current supplied by transistor 426.

The circuit means 700 as a whole also include converter connections. which is supplied with a driving power from the rectifier diode 205. Some The rectified input voltage is made by means of the capacitor 705, why the resulting voltage supplied to the converter is amplitude modulated with a degree of modulation of about 40%; the amplitude the modulated input voltage thus provides the envelope to the pulse ver converter. Resistors 706-709 provide volume control for the tone generator.

The diode 710 passes through the back emf generated by the decay the voltage across the inductance of the converter 300.

The generator means 500 provided with frequency shift input are is shown in Fig. 3 as a special embodiment but can be given one more general form, see Fig. 5. The generator means 500 include three power sources. 520, 521 and 522, a comparator 523, a capacitor C and a resistor R. The power source 520 emits a current of magnitude I and is tinuerly at work. The power source 521 emits the current K1I and is beaten when the output signal of the comparator 523 is logic one. Power source 522 is also turned on when the output signal of the comparator 523 is logic one but emits a current of magnitude K2I or Kal depending on the the similarity of a frequency shift input signal. This relationship is evident from a truth table also shown in Fig. 5.

The comparator 523 is provided with two incoming lines A and B and an output line D. A voltage VREF is via a resistor R. connected to the input line A of the comparator A. The power source 522 is 10 15 8102406-9g 12 connected between line A and a common reference potential such as soil. Capacitor C and current sources 520 and 521 are connected between the input line B the common reference potential. Out- line D, which is located at logic one of the input lines line A is at a higher level than the input line B and at logic zero if the input line A is at a lower level than the input line B, connects the output of the comparator 523 to the power sources 521 and 522.

The frequency shift input signal is also applied to the power source 522.

Capacitor C is discharged by current I from current source 520 and is charged by the current K1I from the current source §21. Because K1I is proportional to I, the net charging current can be written as (K1-1) I, The three voltage levels that can occur across the resistor R are 0.

RKZI or RK3I and depends on whether the frequency shift signal is present.

The voltage thresholds between which capacitor C must oscillate are thus either 0 and RKZI or 0 and RK3I.

For the time interval during which capacitor C is charged at logic one as output signal from capacitor 523 applies to: Å VRC KZRIC 1 <2 = = = RC Iuppl (K1-1) I (K1-1) ... msn -__ tupel (1) Furthermore, applies g AVRC KZRIC url I = = K RC (2) I 2 t url The period thus amounts to 1 < 2 +1 tuppl: + turl = É: _: T ' 1 H1 2 = 1 + --- K RC = RC K1-1 (3) The frequency thus applies K1-1 _frekv = g g 1 <11 <2Rc and in the frequency shift case K -1 'K1K3RC For the heart rate ratio applies (HRS) freq (5) * <2 Kl-1 = R- * (5) K1K2 K1-1 10 15 20 25 30 8102406-9 13 From the above it appears first of all that the frequency and pulse the ratio is determined by the values of the resistor R and the capacitor C and on the relationship between I and K1I and, secondly, to change of frequency by changing R, C or K2 does not affect pulse rate. IN If discharge of capacitor C is taken as a starting point, the oscillator works as follows. The voltage across the condenser tower C and on the input line B are discharged from the power source 520 so that it becomes less than the voltage VREF on the input line A. This to change the output of comparator 523 to logic one. This this starts the current source 521 with the current K1I. An upload (K1-1) I then charges the capacitor D. The logic one from the comparator 523 also starts the power source 522 with the current K2I or K3I whereby the voltage on the input line A is increased to one voltage corresponding to RK2I resp. RK3I plus VREF. When the capacitor C charged to the point where the comparator's input line B becomes more positive than the input line A, the output signal of the comparator 523 passes to zero. The current source 522 is then switched off, and the voltage on in ~ the overhead line A becomes VREF again. Furthermore, the power source 521 is also closed off, and the power source 520 initiates a discharge of the capacitor C from a voltage equal to RKZI + VRÉ; or RK3I + VREF down to one voltage below VREF at which point the comparator output signal again transitions to logic one state, after which the oscillation resumes repas. It is thus obvious that the voltage swing across the capacitor 2I or KSI and that the charging and discharging speeds of capacitor C are determined tower is determined by the current K emitted by the current source 522 mes of the power sources 521 resp. 520. The period of the oscillation thus constitutes is a function of the resistance-fobh capacitor values plus current the ratio of the sources (all K-terms constant). Since the current the sources are related to each other, in addition, the current from them vary over a wide range without affecting the frequency of work provided that said conditions are maintained. Supply voltage variations will thereby have minimal effect on the oscillator working frequency.

Claims (2)

8102406-9 14 Patent claims 1, a tone amplifier circuit comprising input terminals for receiving ring signals, an electroacoustic transducer (300) for generating an audible output signal, an oscillation generator means (500) for activating the electroacoustic transducer, and a power conversion means (200), which responds to the ring signal over the input terminals and is arranged to supply energy to the tone generator circuit, characterized in that the tone generator circuit also comprises first constant current generators (223- -226) connected to the power conversion means (200) arranged to supply voltage reference means levels (500); that the generator means comprise other constant current generators (501-504, 509-511) and a transistor pair (506, 507) connected to an RC network (505, 51%); that the second constant current generators are connected as current mirrors to one (223) of the first constant current generators; and that the other constant current generators supply energy to said transistor pairs, which is differentially connected and connected to the RC network so that in its active state it conducts current with a frequency determined by the RC network and with a pulse ratio determined by the ratio between the currents. of two (503, 504) of the other constant current generators. 2. A tone generator circuit according to claim 1, characterized in that the first constant current generators comprise a number of transistors connected as current mirrors, the emitters of which are connected via resistors to either line in the output line pairs of the power conversion means (200).