WO1988002198A1

WO1988002198A1 - Retrofit remote control apparatus

Info

Publication number: WO1988002198A1
Application number: PCT/AU1987/000312
Authority: WO
Inventors: Thomas Michael Kenny; Roberto Enzo Di Biaggio
Original assignee: Thomas Michael Kenny; Roberto Enzo Di Biaggio
Priority date: 1986-09-16
Filing date: 1987-09-16
Publication date: 1988-03-24
Also published as: AU7964787A; JPH01501193A; AU610522B2

Abstract

A retrofit remote control apparatus (10) comprising a transmitter (12) configured to transmit coded data, a receiver (14) configured to receive the coded data, a logic means (15) connected to the receiver (14) to decode the coded data, a resistance ladder network (16) connected to the logic means (15), the resistive ladder network (16) having a signal input (18) with a substantially constant input impedance and a signal output (20) with a discretely variable output impedance, the output impedance of the resistive ladder network (16) being controlled by the logic network (15).

Description

TITLE RETROFIT REMOTE CONTROL APPARATUS DESCRIPTION The present invention relates to a retrofit remote control apparatus. The invention is particularly envisaged for use in remotely controlling the audio volume output of an audio amplifier although it is to be understood that it is of general applicability.

FIELD OF THE INVENTION In general, audio equipment are constructed either with or without remote control apparatus. In the former use an in built remote control apparatus may have various features including say audio volume control. In the latter case a remote control apparatus may be fi.tted to the audio equipment only by modifying the audio equipment.

Where the remote control apparatus is fitted by modifying the audio equipment the fitting requirements generally vary from one piece or brand of audio equipment to the next. Thus making it difficult to enable one design of remote control apparatus to be fitted by modification to a variety of audio equipment.

Prior art remote control apparatus, both fitted and in built, generally have active components present in a control path used for remote control. In order to maintain fidelity of sound in the audio equipment prior art remote control apparatus operate relatively quickly with relatively fast slew rate components. Such requires relatively larger amounts of electrical power and hence such prior art remote control apparatus are generally not suited to operation from - 2 - battery electrical power.

SUMMARY OF THE INVENTION The present invention relates to a remote control apparatus operable at relatively low electrical power levels and capable of retrofitment to a variety of audio amplifiers.

In accordance with the present invention there is provided a retrofit remote control apparatus characterised in that it comprises a transmitter configured to transmit a signal, a receiver configured to receive the signal, a logic means connected to the receiver to interpret the signal, a signal attenuation means controlled by the logic means and arranged to be connected to a TAPE LOOP facility of an audio amplifier and configured to attenuate signals fed to a power amplifier of the audio amplifier. Preferably, the signal input and the signal output are connected to a tape loop facility of an audio amplifier. Preferably, the retrofit remote control apparatus is configured to remotely control the audio output volume of the audio amplifier. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic circuit diagram of an audio amplifier having a tape load facility and a retrofit remote control apparatus in accordance with the present invention connected to it together with a tape deck? Figure 2 is a circuit diagram of a transmitter of the retrofit remote control apparatus of Figure 1; Figure 3 is a 'block diagram of a receiver and resistive ladder network of the retrofit remote control apparatus of Figure 1; - 3 -

Figure 4 is a circuit diagram of the receiver and resistive ladder network of Figure 3; and

Figure 5 is a schematic circuit diagram of the resistive ladder network of Figures 3 and 4. DESCRIPTION OF THE INVENTION

In Figure 1 there is shown a retrofit remote control apparatus 10 comprising a transmitter 12, a receiver 14, a logic means 15, a signal attenuation means 16, a signal input 18 and a signal output 20. The signal input 18 is arranged to be connected to a TAPE

LINE OUT output 22 of an audio amplifier 24 and the signal output 20 is arranged to be connected to a TAPE LINE IN input 26 of the audio amplifier 24.

The audio amplifier 24 comprises a conventional TAPE LOOP facility with a switch 28. The switch 28 is connected between an audio preamplifier 30 with audio inputs 32 and an audio power amplifier 34 with an audio power output 36 connected to a loud speaker 38.

The switch 28 is connected to switch from a normal mode in which the audio preamplifier 30 is connected directly to the audio power amplifier 34, to a tape monitor mode in which the audio power amplifier 34 is connected to the TAPE LINE IN input 26. in the latter mode the TAPE LINE OUT output 22 and the TAPE LINE IN input 26 are conventionally connected directly to a tape deck 40 at an input 42 and an output 44 respectively.

The tape deck 40 is schematically represented by a record amplifier 46 connected to drive a record head 48, a play head 50 connected to a preamplifier 52 to amplify signals - 4 - read by the play head 50. A PLAY/RECORD switch 54 is provided to feed a signal to the output 44 _r which switch 54 is used to monitor either the record head 48 or the play head 50. In the present invention the input 42 and the output 44 of the tape deck 40 are substituted with the signal input 18 and the signal output 20.

The facility is referred to as a TAPE LOOP facility since all signals from the preamplifier 30 in the tape monitor mode are intended to pass from the TAPE LINE OUT output 22 to the TAPE LINE IN input 26 through whatever is connected to said output 22 and said input 26.

The retrofit remote control apparatus 10 also conveniently comprises a line output*56 connected to the signal input 18 and a line input 58 connected via a switch means 60 to the resistive ladder network. The switch means 60 is operable to connect the tape deck 40 into and out of circuit with the retrofit remote control apparatus 10. The transmitter 12 conveniently comprises a remote control transmitter integrated circuit 70, such as, for example, a Motorola MC 145026. The remote control transmitter 70 comprises a transmitter address word means formed from address word inputs 72 connected to a DIP switch 74. The DIP switch presets a binary address word into the remote control transmitter 70 so as to uniquely identify the transmitter 12-.

The remote control transmitter 70 also comprises a data word means formed from data inputs 76 and 78 each of which are connected to a push button switch 80 and 82 respectively. - 5 - The push button switches 80 and 82 are connected to a transmit enable input 84 of the remote control transmitter 70. A further push button switch 86 is connected to the transmit enable switch 84. The data inputs 76 and 78 are connected to a positive power rail 88 via resistors 90 and 92 respectively. The data inputs 76 and 78 both have logic high values when none of the switches 80, 82 or 86 are depressed or when only the switch 86 is depressed and separately take a logic low value when the switches 80 and 82 are respectively depressed. Upon depression of one of the switches 80, 82 or 86 the transmit enable input 84 is activated and the logic values at the data inputs 76 and 78 are read into the remote 'control transmitter 70 together with the address word from • the DIP switches 74. The remote control transmitter 70 then serializes the address word and the data word and outputs them to a data output 94.

The frequency of serialization of the address word and data word is set by two resistors 96 and 98 and a capacitor 100. Preferably, capacitors 102 and 104 are connected in parallel with the resistors 90 and 92 respectively so that the logic levels at the data inputs 76 and 78 remain constant whilst the transmit enable input 84 is deactivated. A time constant of 100ms for the resistor capacitor configuration has been found to be suitable.

The transmitter 12 also comprises an RF oscillator 106. having a transistor 108, such as for example a 2SC 1907, a parallel tunnel circuit 110 and an input 112. The data output 94 is connected to directly modulate a base input of - 6 - the transistor 108 via the input 112.

Preferably, the RF oscillator 106 is configured to operate at UHF frequencies, in which case an inductor 114 of the tuned circuit may be formed from P.C.B. tracks and no extend antenna is required for the transmitter 12. Accordingly, the transmitter 12 has a very low power output (in the range of a few micro watts) and very low power consumption. Accordingly, the transmitter 12 may conveniently be powered from a relatively small battery, such as, for example, a small 216 type nine volt DC battery.

It is envisaged that the transmitter 12 could be an infrared or ultrasonic frequency transmitter 12 or the like. Although an RF frequency transmitter 12 is preferred since such provides for greater range of operation and which does. not require line-of-sight operation.

The transmitter 12 is contained in a housing, conveniently made of plastics material and dimensioned to be portable and hand held. The retrofit remote control apparatus 10 also comprises a receiver 14 as shown in Figures 3 and 4. The receiver 14 comprises an RF frequency demodulator 120 tuned to the same frequency as the tuned circuit 110 of the transmitter 12. The demodulator 120 extracts the serialized address word and data word from the received RF signal. The receiver 14 also comprises a data shaper 122 connected to the demodulator 120 and configured to square up the demodulated signal. The data shaper 122 comprises an output 124 having on it a serialized words similar to those generated by the remote control transmitter 70. - 7 - The receiver 14 also comprises a remote control receiver 126 integrated circuit, such as, for example, a Motorala MC 145027. The remote control receiver 126 comprises an data input 128 connected to the output 124. The remote control receiver 126 comprises an address word means formed from binary address word inputs 130 connected to a DIP switch 132 in similar manner to the remote control transmitter 70.

The remote control receiver 126 also comprises a data word means formed of two data outputs 134 and 136 and a valid data output 138.

Two RC timing networks 140 and 142 are connected to the remote control receiver 126 to set the receive data rate. The receive data rate is preferably matched to the transmit data rate.

The address word means of the remote control receiver 126 reads in the serialized words to the data input 128 and compares the address word of the data (first received) with the binary address word provided at the binary address word inputs 130. Upon detection of equality between the received address word and the address word of the DIP switch switches 132 the data word means is controlled to set the data word to the data outputs 134 and 136.

It is intended that a high at the data output 134 correspond to closure of the switch 86, a low at the data output 134 correspond to closure of the switch 80 and a low at the data output 136 correspond to a closure of the switch 82. The valid data output 138 is set active upon detection of a watch in the two above mentioned address words. - 8 - The receiver 14 also comprises a logic means 15 connected to the data outputs 134 and 136 and to the valid data output 138. The logic means 15 comprises, a clock generator 150 counter 152 and a comparator network 154. The clock generator 150 comprises an oscillator conveniently •formed from a schmitt trigger 156 and having a trigger input 160 connected to the valid data output 138. The clock generator 150 has a clock output 162 connected to a clock input 164 of the binary up/down counter 152. The clock generator 150 comprises resistors 166 and 168 and capacitors 170 and 172 configured to produce a single high pulse for an active signal at the valid data output 138 having a relatively short duration, say less than 0.3 seconds, and to produce a plurality of high pushes when the _ signal at the valid data output 138 remains 'active for longer than 0.3 seconds.

The binary up/down counter 152 comprises an input 174 connected to the data output 134. The input 174 is configured to control the direction in which binary counting is carried out. A high at the input 174 causes the counter 152 to count up and vice versa for a low. The counter 152 also comprises a preset enable -input 176 connected via an inverter 178 to the data output 136. A high at the preset enable input 176 causes the counter 152 to read a plurality of present inputs.180 and to set a plurality of outputs 182 equal to the logic values at the present inputs 180.

In the present embodiment the present inputs 180 are all grounded. The outputs 182 are connected to the comparator network 154. The comparator network comprises a first comparator 184 comprising two inverter .gates 186 and 188 and NAND gate 190. The inverter 186 is connected to a carry out output 192 of the counter 152 and goes high to detect when all of the outputs 182 are high.

The NAND gate 190 is connected to the input 174 and detects when all of the outputs 182 are high and a high is registered at the input 174. That is the NAND gate 190 detects when the counter is about to change to count at the outputs 182 from 1111 to 0000.

The inverter 188 connects the NAND gate 190 to the capacitor

172 of the clock generator 150 to inhibit the clock _In the above mentioned state.

Accordingly, the first comparator prevents the counter from counting up from 1111 to 0000.

The comparator network also comprises a second comparator 194 comprising an inverter 196 fed via diodes 198 from the outputs 182 and from a diode 200 connected to the input 174. The inverter 196 is also connected to the capacitor 172 to disable the clock generator, by setting the capacitor 172 high, in the event that all of the outputs 182 are low and the input 174 is low. That is the second comparator 194 prevents the counter 152 from counting from 0000^" to 1111. The outputs 182 are also connected to the signal attenuator means 16. In the present embodiment the signal attenuator means is in the form of a resistor ladder network 16 conveniently comprising four inverters 201, one for each of - 10 - the outputs 182, to produce a complementary output 202.

The resistive ladder network 16 also comprises two banks 203 of eight bilateral lateral switches 204 (Figure 5) each of eight bilateral lateral switches 204 of eight bilateral lateral switches 204 (Figure 5) , each of eight bilateral lateral switches 204 being housed in two integrated circuits (IC's) 206 and 208 (Figure 4).

The IC 206 of each of the banks 203 is connected to the complementary outputs 202 and the IC 208 of each of the banks 203 is connected to the outputs 182, as shown in Figure 5.

Each of the bilateral lateral switches 204 of each of the IC's 206 and 208 is connected in parallel with a resistor 210, 212, 214, 216. The values of the resistors 210 to 216 increase binomially, for ^"example R, 2R, .-4R and 8R, respectively where R is an arbitrary resistance. The resistors 210 having a value of R is connected via one of the bilateral switches 204 to the least significant bit LSB of the output 182, the resistors 212 to the next most significant bit MSB and so on. the resistive ladder network 16 has an input impedance which is the same of the resistances of the resistors 210 to 216 which are not shorted out by the bilateral switches 204. It will be seen that the input impedance is substantially constant. Such occurs since for each resistance 210 to 216, connected to the IC's 206, that are shorted out, the same resistance 210 to 216 connected to the IC's 208 comes into circuit. The output impedance of the resistive ladder network 16 is - li ¬ the impedance between the output 20 and ground 218. The output impedance varies from about OR when all the outputs 182 are all low to about 15R when all the outputs 182 are high. There being 16 discrete steps of substantially equal resistance change.

It is important that the resistor of value R be connected to the LSB of the output 182 and the resistor of value 2R to the next significant bit and so on, so that as the binary counter 152 counts up or down there is produced a change in output impedance of only about R and no more. Otherwise an increase ^' in count could produce a vacation in output impedance.

Thus the resistive ladder network 16 operates as a discretely variable potentiometer with substantially constant input impedance and discretely variable output impedance.

It is important to note that such would not be the case if the complementary driven IC's 208 were not included, as in such case the input impedance and the output impedance are equal. However, by inverting each of the binary outputs 182 and controlling an inverted ladder symmetrically constant input impedance is achieved.

In order to function properly the preamplifier 30 of the audio amplifier 24 must drive a substantially constant load. The resistive ladder network- 16 then simply divides the voltage at the signal input 18 into 16 steps and produces a proportional voltage at the signal output 20. Such proportional voltage is amplified by the power amplifier 34 and produces a proportionate decrease in the volume of sound in the loud speaker 38.

The drawing of Figure 1 depicts only a single audio channel but more duplication thereof represents a stereo situation as compatible with the stereo restive ladder 16 of Figure 4. It is envisaged that the data output 136 could be used to set the outputs 182 to a preset value independent of the present inputs 180, so that the outputs 182 could then be reset to their previous values. In use, , the retrofit remote control apparatus 10 of the present invention has its signal input 18 connected to the TAPE LINE OUT output 22 of the audio amplifier 24 and its regional output 20 connected to the TAPE LINE IN input of the audio amplifier 24. The tape deck 40 may be connected to the line output 56 and the line input 58 via the 'input 42 and the output 44 respectively. Accordingly, the audio amplifier 24 may continue to have as many audio inputs as would be the case if the retrofit remote control apparatus 10 was not used. To connect the apparatus 10 into circuit the tape monitor 28 is moved to the tape monitor mode.

The switch 28 is to be left in this mode and no other monitor switches operated in using other audio sources connected to the audio inputs 32. In such manner a signal from the audio inputs 32 is amplified by the preamplifier 30 attenuated by the resistive ladder network 16- and amplified by the power amplifier 34.

The amount of attenuation may be altered by depending one of the switches 80, 82 or 86 of the transmitter 12. The switch 80 causes an increase in attenuation up to a maximum, the switch 86 causes a decrease in attenuation down to a minimum and the switch 82 causes setting of the attenuation to a preset ^"value, as set by the preset inputs 180. The switches 80, 82 and 86 are conveniently referred to as DOWN, MUTE AND UP respectively, which describe the effect that they each have on the sound volume at the loud speaker 38.

On depressing one of the switches the remote control transmitter 70 reads in the address word and the data word and serially sends it to the output 94 switch directly modulates the transistor 108. The oscillator 106 modulates the serialised words onto an RF carrier and transmits it via the indicator 114.

The receiver 14 receives the signal via an antenna 230 and the demodulator 120 extends the serialized words and the shaper 222 squares up the serialized words and inputs then to the remote control receiver 126 via data input 128. The remote control receiver 126 compares the received address word and compares it to that of the DIP switches 132. Where there is a match in the address the remote control receiver 126 sends an active signal on the valid data output 138 which signal activates the clock generator 150.

Simultaneously, the data word is output on the data output 134 and 136.

The decoder 152 reads the inputs 174 and 176 when its clock input 164 is active.

Where the switch 80 or 82 or 86 is depressed for greater than say 0.3 seconds, the clock generator generates pulses at the rate of 3Hz to provide an auto repeat function. Depending on which switch 80, 86 or 82 was pressed the count (that is the bit value at the output 182) is decreased, increased or preset, respectively as described hereinabove. The comparator network 154 checks the outputs 182 and the inputs 174 and 176 and prevents the counter from counting from 1111 to 0000 and from 0000 to 1111. The audio volume is prevented from going from maximum to minimum and vice versa where the up (or down) key is continued to be pressed. The binary value of the output 182 causes shorting of the resistors 210 to 216 in the banks 203 such as to maintain a constant input impedance as described.

The switch 60 may be operated to connect the tape deck 40 in series with the line output 5'6 and the line input 58. By use of the apparatus 10 of the present invention control " of the audio volume of an amplifier 24 may be achieved. The apparatus may be retrofitted to virtually any amplifier 24 having a TAPE LOOP facility. Thus, the apparatus requires so complicated installation and does not require alteration for use with different designs of amplifiers 24.

The attenuation provided by the resistive ladder network 16 is substantially passive and so- high slew rate components, which draw relatively loose electrical power, are not required. Accordingly, the ladder network 16 may be battery powered.

The audio volume control afforded by the apparatus 10 does not exceed the volume set by a conventional volume control of the power amplifier 34. It is envisaged that a steerage resistor may be connected across the signal output 20 to ground to produce an antilog type attenuation.

All or some of the switches 80, 82 and 86 of the transmitter 12 could be replaced with remote sensors connected to the transmitter 12 and arranged to detect, for example, particular sounds or events. The sounds may include the ringing of a telephone or doorbell or the breaking of a pane of glass. The events may include the opening of a door or the like. In such manner the apparatus 10 may be used to automjatically increase or decrease the volume of sound from the loudspeaker 38 to indicate the occurrance of an event. In such case the mute could be set to produce maximum volume at the loudspeaker 3'8 upon detection of the breaking of the pane of glass.

Also the apparatus 10 could be arranged to detect the sound output of the loudspeaker 38 and to prevent same exceeding a volume set by the remote sensor.

Modifications and variations such as would be apparent to a skilled addressee are deemed within the scope of the present invention.

Claims

CLAIMS 1. A retrofit remote control apparatus characterised in that it comprises a transmitter configured to transmit a signal, a receiver configured to receive the signal, a logic means connected to the receiver to interpret the signal, a signal attenuation means controlled by the logic means and arranged to be connected to a TAPE LOOP facility of an audio amplifier and configured to control the level of the sound output from the audio amplifier.

2. A retrofit remote control apparatus according to Claim 1, characterised in that the signal attenuation means comprises an input arranged to be connected to a TAPE LINE OUT output of the audio amplifier and a signal output arranged to be connected to a TAPE LINE IN input of the audio amplified, the signal attenuation means being configured to attenuate . audio signals received at the signal input to produce attenuated audio signals at the signal output.

3. A retrofit remote control apparatus according to Claims 1 or 2, characterised in that the transmitter comprises a transmitter address word means and a data word means connected to modulate an oscillator to radiate said signal, said signal comprising a transmitter address word and a data word modulated upon a carrier, the address word being preset to a desired value to uniquely identify the transmitter.

4. A retrofit remote control apparatus according to Claim 3, characterised in that one or more switches are provided in or attached to the transmitter to alter the data word.

5. A retrofit remote control apparatus according to Claims 3 or 4, characterised in that the receiver comprises a demodulator configured to demodulate the signal to retrieve the transmitter address word and data word, a receiver address word means connected to the demodulator to compare the transmitter address word to a receiver address word and means to generate a signal at a valid data output of the receiver address word means when the transmitter address word and the receiver address word coincide.

6. A retrofit remote control apparatus according to Claim 5, characterised in that logic means also comprises a counter connected to a data word means of the receiver, a dash clock means connected to the valid data output and configured to generate a clock signal at a clock output, a counter connected to the data word means of the receiver and the clock output, the counter comprising a plurality of outputs whose logic values represent a count of the counter," the count being increased or decreased depending under control of the data word means of the receiver and the clock output.

7. A retrofit remote control apparatus according to Claim 6, characterised in that the logic also comprises a comparator means connected to the plurality of outputs of the counter and to the data word means- of the receiver and configured to inhibit the counter where the count reaches a maximum of a minimum count such that said count may not increase above the maximum count or decrease below the minimum count.

8. A retrofit remote control apparatus according to Claims 6 or 7, characterised in that the clock means is configured to produce a repeated signal at the clock output where the valid data output remains active for greater than a predetermined period of time.

9. A retrofit remote control apparatus according to any one of the preceding claims, characterised in that the signal attenuation means is a resistance ladder network connected to the logic means, the resistive ladder network having a signal input with a substantially constant input impedance and a signal output with a discretely variable output impedance, the output impedance of the resistive ladder network being controlled by the logic network.

10. A retrofit remote control apparatus according to claim

9 , characterised in that the resistive ladder network comprises a plurality of series connected resistors with an

• electronic switc means connected across each of the resistors, the signal output being connected to the series connected resistors at a location intermediate of the length thereof, the electronic switch means being controlled to short circuit some of the resistors to vary the impedance between the signal input and the signal output and the impedance between the signal output and ground such that the number of resistors shorted circuited and the number of resistors conducting is constant.

11. A retrofit remote control apparatus according to claim

10, characterised in that the resistors have values which increase or decrease binomially between the signal input and the signal output and between the signal output and ground.

12. A retrofit remote control apparatus according to claim 10 or 11, characterised in that it comprises a binary counter having outputs including a LSB and a MSB, a - plurality of inverters connected to the outputs to generate complementary outputs, the outputs being connected to one half of the resistors and the complementary outputs being connected to another half of the resistors.

13. A retrofit remote control apparatus according to Claims 4 or 9 to 12, characterised in that the one or more switches are in the form of one or more remote sensors.

14. A retrofit remote control apparatus according to Claim

13, characterised in that the remote sensor is arranged to detect a sound, the remote sensor configured to become active in the event that the sound exceeds a predetermined volume.

15. A retrofit remote control apparatus according to Claim

14, characterised in that the remote sensor, is arranged ^'to detect a sound from a telephone handset.

16. A retrofit remote control apparatus according to Claim 14, characterised in that the remote sensor is arranged to detect a sound from a doorbell.

17. A retrofit remote control apparatus according to any one of the preceding claims, characterised in that it comprises a line output and a line input arranged to have a source of audio signals connected to them and a switch means connected to divert audio signals from the source of audio signal to the TAPE LINE IN input.