CA2110031C - Digital sound level control apparatus - Google Patents
Digital sound level control apparatusInfo
- Publication number
- CA2110031C CA2110031C CA002110031A CA2110031A CA2110031C CA 2110031 C CA2110031 C CA 2110031C CA 002110031 A CA002110031 A CA 002110031A CA 2110031 A CA2110031 A CA 2110031A CA 2110031 C CA2110031 C CA 2110031C
- Authority
- CA
- Canada
- Prior art keywords
- signal
- digital
- pcm
- circuit
- control apparatus
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M9/00—Arrangements for interconnection not involving centralised switching
- H04M9/002—Arrangements for interconnection not involving centralised switching with subscriber controlled access to a line, i.e. key telephone systems
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03G—CONTROL OF AMPLIFICATION
- H03G7/00—Volume compression or expansion in amplifiers
- H03G7/007—Volume compression or expansion in amplifiers of digital or coded signals
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M9/00—Arrangements for interconnection not involving centralised switching
- H04M9/002—Arrangements for interconnection not involving centralised switching with subscriber controlled access to a line, i.e. key telephone systems
- H04M9/008—Multiplex systems
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04M—TELEPHONIC COMMUNICATION
- H04M3/00—Automatic or semi-automatic exchanges
- H04M3/40—Applications of speech amplifiers
Abstract
A digital sound level control apparatus for adjusting the reception sound level from all telephone circuits to a substantially fixed level comprises a region discrimination circuit for discriminating PCM data input from a PCM
conversion section, the data having a segment code for compressing and decompressing a digital audio signal, including an intrinsic variation signal, abasic normalization level signal, and a coding threshold value; a multiplicationcircuit for outputting an input level signal of 12 bits, an addition circuit; a register for holding a pad multiplication value corresponding to a reception circuit; another multiplication circuit for multiplying the input level signal by the pad multiplication value to output an output level signal for outputting sound of a predetermined sound level; and a comparison region discrimination circuit, a subtraction circuit, a division circuit, and a register for regenerating an 8-bit digital signal from the output level signal.
conversion section, the data having a segment code for compressing and decompressing a digital audio signal, including an intrinsic variation signal, abasic normalization level signal, and a coding threshold value; a multiplicationcircuit for outputting an input level signal of 12 bits, an addition circuit; a register for holding a pad multiplication value corresponding to a reception circuit; another multiplication circuit for multiplying the input level signal by the pad multiplication value to output an output level signal for outputting sound of a predetermined sound level; and a comparison region discrimination circuit, a subtraction circuit, a division circuit, and a register for regenerating an 8-bit digital signal from the output level signal.
Description
21100~1 -DIGITAL SOUND LEVEL CONTROL APPARATUS
This invention relates to the main unit of a key telephone system including a segment coder for companding (compressing and decompressing) a 5 digital audio signal, and more particularly to a sound level control apparatus for use with an apparatus of the type described above.
Figure 1 shows a conventional monitor circuit of a digital audio apparatus.
A conventional digital sound level control apparatus of the type 10 mentioned above includes, as disclosed in Japanese Patent Application No.
72457/1986, entitled "Monitor Circuit" shown in Figure 1, a circuit for adjusting a sound output level by sending a code signal to a monitor section 52 from a soundlevel adjusting switch 54 and multiplying a pulse code modulation (PCM) audio signal output from a monitor signal extraction circuit 58 by the code signal to 15 define the monitor sound level through a sound level conversion memory 57, a digital audio convertor 56, and an analog amplifier 55.
The conventional digital sound level control apparatus includes a ROM
in which a predetermined conversion table is stored. Accordingly, the conventional digital sound level control apparatus is disadvantageous in that 20 much labor and time are required to write the conversion table into the ROM
upon assembly of a digital key telephone system and in that, once the ROM is incorporated into a telephone apparatus, the sound level cannot be varied in conformity with a circuit with which the telephone apparatus is used.
It is therefore an object of the present invention to provide a digital 25 sound level control apparatus which eliminates the setting of a contrast table between sound levels and conversion codes into a ROM.
According to a first embodiment of the invention, there is provided a digital sound level control apparatus for the main unit of a digital key telephone system, the main unit including a circuit control section for each telephone circuit, 30 a PCM conversion section having a segment coder for compressing with a ,u-LawPCM characteristic for each telephone circuit, a main control section for designating a pad multiplier which defines an attenuation value corresponding to A - 1 - ~
the employed telephone circuit, a digital sound level control apparatus for eachtelephone circuit and digital time switching means for switching speech paths, the digital sound level control apparatus comprising:
means for decompressing a received ,u-Law digital PCM signal, means for multiplying the decompressed digital signal by said designated pad multiplier, means for compressing the multiplied value to a ,u-Law PCM digital signal, and means for outputting the,u-Law digital PCM signal to the digital time switching means.
According to a second embodiment of the invention, a digital sound level control apparatus is provided for the main unit of a digital key telephonesystem, the main unit including a circuit control section for each telephone circuit, a PCM conversion section having a segment coder for compressing with a ,u-Law PCM characteristic for each telephone circuit, a main control section for designating a pad multiplier which defines an attenuation value corresponding tothe employed telephone circuit, a digital sound level control apparatus for eachtelephone circuit and digital time switching means for switching speech paths, the digital sound level control apparatus comprising:
first discrimination means for discriminating a segment region of a,u-Law PCM conversion characteristic polygonal line from a segment region signal of a PCM input data signal which is outputted from the PCM conversion section, the PCM input data including a polarity signal, a segment region signal and a step signal;
first calculation means for calculating a first level signal which is a data value before compression using the output signal of the first segment region discrimination means and the step signal of the PCM input data signal;
multiplication means for multiplying a pad multiplier by the first level signal to output a second level signal;
second segment region discrimination means for discriminating a segment region by comparing the second level signal with the coding threshold -values of segment regions based on the segment compression and decompression characteristic;
second calculation means for calculating a step signal based on the second level signal, the coding threshold signal and the intrinsic variation amount 5 per step of the segment region;
register means for forming a ~-Law PCM digital signal by combining the original polarity signal, the calculated segment region signal and the calculated step signal.
The first level signal of the digital sound level control apparatus 10 described above may be obtained by adding the product of the intrinsic variation amount per step of a segment region and the step signal to the basic normalization level signal of said segment region, or by adding the product of the intrinsic variation amount per step of a segment region and the step signal to the coding threshold value of said segment region.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:
Figure 1 is a block diagram of a monitor circuit of a conventional digital sound level control apparatus;
Figure 2 is a block diagram of an embodiment of the main unit of a key telephone system; and Figure 3 is a block diagram of pad conversion section 13 shown in Figure 2.
With reference to Figures 2 and 3, the main unit of key telephone system 1 comprises circuit control section 11, PCM conversion section 12, main control section 15, pad conversion section 13 and time divisional switch 14.
The present invention is incorporated into pad conversion section 13 and main control section 15.
Circuit control section 11 serves as an interface to telephone circuit 2 and reports to main control section 15 the classification of telephone circuits employed for incoming telephone calls. PCM conversion section 12 converts an incoming analog data signal into a ,u-Law PCM digital signal. Pad conversion section 13 outputs data signal Do which is modified from PCM input data signal ..... ,,~
-Dl from PCM conversion section 12 to digital data having a controlled sound level by decompressing, multiplying by pad multiplier Pd sent from main control section 15 and compressing to ,u-Law PCM digital data. Main control section 15 outputs multiplier Pd signal to pad conversion section 13 corresponding to the employed 5 incoming telephone circuit by discriminating by notification from circuit control section 11. Time divisional switch 14 switches telephone calls by switching the connection of the PCM highway.
PCM input data signal Dl is an 8-bit signal wherein the MSB
corresponding to the eighth bit serves as polarity signal P, the three bits 10 corresponding to the seventh to fifth bits serve as a segment region (referred to as region signal A hereafter) which identifies a segment, and the remaining fourbits corresponding to the fourth to first bits serve as step signal bits S
representative of a position in a segment.
Region signal A includes intrinsic variation signal A1 representative of 15 the variation amount per step of the level value in the segment region beforecompression, basic normalization level signal A2 (4,191 in region 8; 2,079 in region 7; 1,023 in region 6 and the like) representative of a reference point for each segment region before compression, and coding threshold value A3 (4,063 in region 8; 2,015 in region 7; 991 in region 6 and the like) representative of the 20 start point of each region before compression.
Pad conversion section 13 converts compressed PCM input data into data of the level before compression with reference to the basic normalization level signal before compression, multiplies the data of the thus converted or decompressed level by a pad multiplier to convert the data into a predetermined 25 sound volume, compresses the volume signal again, and outputs the thus compressed volume signal to the time divisional switch 14. Pad conversion section 13 includes register 31 for temporarily storing input data signal Dl, another register 32 for temporarily storing the pad multiplier signal Pd, regiondiscrimination circuit 33 for discriminating region signal A in PCM input data 30 signal Dl and dividing region signal A into intrinsic variation signal A1, normalization reference level signal A2 and coding threshold value A3, multiplication circuit 34 for multiplying step signal S in PCM input data Dl by `` 21100~1 -intrinsic variation amount signal A1, addition circuit 35 for adding basic normalization level signal A2 to the output signal of multiplication circuit 34 to output level signal Ll, another multiplication circuit 36 for multiplying input level signal Ll by pad multiplier signal Pd to produce output level signal LO, region comparison discrimination circuit 37 for comparing output level signal LO and coding threshold value A3 to determine to which region output level signal LO
corresponds, and outputting region signal A' based on the determination, subtraction circuit 38 for subtracting coding threshold value A3 intrinsic to a region determined from region signal A from output level signal LO, division circuit 39 for dividing the output of subtraction circuit 39 by intrinsic variation signal A1 to output step signal S', and register 40 for temporarily storing polarity signal P, region signal A' and step signal S'.
Operation of the embodiment will now be described below.
Analog audio data received from telephone circuit 2 are inputted by way of circuit control section 11 and converted into a PCM signal by PCM
conversion section 12. In this instance, circuit control section 11 determines whether the received call has originated from an extension line or another subscriber line and notifies the result of the determination to main control section 15.
Meanwhile, PCM coded audio data are outputted by PCM conversion section 12 to pad conversion section 13 as input data signal Dl. Separately, depending on the result of the determination of either an extension line or another subscriber line previously notified to main control section 15, pad multiplication value signal Pd representative of an attenuation amount is sent from main control section 15 to pad conversion section 13, and PCM output data signal Do for which the sound volume difference has been adjusted is outputted to time divisional switch section 14 in which a PCM highway is exchangeably connected.
The sound level difference among calls from extension lines and other subscriber lines can thus be eliminated by the way that multipliers to designateattenuation amounts are set and stored in main control section 15 in such a manner that the attenuation amount is, for example, 0 dB for a call received from outside line 2 and 6 dB for a call received from an extension line.
211~0~1 -The operation of pad conversion section 13 of the embodiment will now be described.
PCM input data signal Dl from PCM conversion section 12 is inputted to 8-bit register 31 while pad multiplier value signal Pd for determination of the 5 attenuation amount from main control section 15 is inputted to 4-bit register 32.
Region discrimination circuit 33 discriminates a region from region signal A in PCM input data signal Dl inputted to register 31 and outputs basic normalization level signal A2 intrinsic to the region, intrinsic variation amount signal A1 intrinsic to the region determined from region signal A, and coding 10 threshold value A3.
Multiplication circuit 34 multiplies intrinsic variation value signal A1 by step signal (bits 4 to 1) S of PCM input signal Dl, and the product is added to basic normalization signal A2 by addition circuit 35. The sum of the addition isoutputted as input level signal Ll. Meanwhile, polarity signal P (bit 8) of PCM
15 input data signal Dl is not inputted to region discrimination circuit 33 but is outputted as is as a polarity signal of PCM output data signal Do.
The pad multiplication value signal Pd sent from main control section 15 is inputted to and then outputted from register 32.
Multiplication circuit 36 multiplies input level signal Ll outputted from 20 addition circuit 35 by pad multiplication value signal Pd outputted from register 32 and outputs the result of the multiplication as output level LO.
Segment region comparison discrimination circuit 37, which compares coding threshold value A3 determined from region signal A by region discrimination circuit 33 and output level signal Lo outputted from multiplication 25 circuit 36, determines the region to which output level signal Lo corresponds, and outputs corresponding region signal A' (bits 7 to 5).
Further, the result of the substraction of coding threshold value A3 from output level signal LO by subtraction circuit 38 is divided by intrinsic variation signal A1 determined from region signal A' by division circuit 39, and the 30 result of the division is outputted as step signal S' (bits 4 to 1).
PCM output data signal Do after conversion into a pad value instructed by main control section 15 from polarity signal P (bit 8), region signal A' (bits 7 2110~31 -to 5), and step signal S' (bits 4 to 1) is stored once into and then outputted from register 40.
Meanwhile, main control section 15 outputs pad multiplication value Pd to pad conversion section 13 in accordance with the type of circuit. Where the 5 number of types of circuits involved is great, it may be possible to provide means for setting correspondence tables so that the corresponding pad multiplier may be outputted for each of the types of circuits.
Further, while, in the present embodiment, input level Ll is obtained by the addition of the product between intrinsic variation signal A1 and step signal 10 S to the normalization reference level signal A2, it may be obtained otherwise by the addition of the product of the intrinsic variation amount signal A1 and the step signal S to the coding threshold value A3.
As described above, since region signals and step signals corresponding to the circuits from which calls are received, rather than fixed 15 region signals and step signals, as in the case of a conventional digital sound level control apparatus, are outputted from the digital sound level control apparatus of the invention by calculating the region signal and the step signal,there is an advantage in that the reception sound level can be held substantially constant irrespective of the type of telephone circuit from which a call is received.
A
This invention relates to the main unit of a key telephone system including a segment coder for companding (compressing and decompressing) a 5 digital audio signal, and more particularly to a sound level control apparatus for use with an apparatus of the type described above.
Figure 1 shows a conventional monitor circuit of a digital audio apparatus.
A conventional digital sound level control apparatus of the type 10 mentioned above includes, as disclosed in Japanese Patent Application No.
72457/1986, entitled "Monitor Circuit" shown in Figure 1, a circuit for adjusting a sound output level by sending a code signal to a monitor section 52 from a soundlevel adjusting switch 54 and multiplying a pulse code modulation (PCM) audio signal output from a monitor signal extraction circuit 58 by the code signal to 15 define the monitor sound level through a sound level conversion memory 57, a digital audio convertor 56, and an analog amplifier 55.
The conventional digital sound level control apparatus includes a ROM
in which a predetermined conversion table is stored. Accordingly, the conventional digital sound level control apparatus is disadvantageous in that 20 much labor and time are required to write the conversion table into the ROM
upon assembly of a digital key telephone system and in that, once the ROM is incorporated into a telephone apparatus, the sound level cannot be varied in conformity with a circuit with which the telephone apparatus is used.
It is therefore an object of the present invention to provide a digital 25 sound level control apparatus which eliminates the setting of a contrast table between sound levels and conversion codes into a ROM.
According to a first embodiment of the invention, there is provided a digital sound level control apparatus for the main unit of a digital key telephone system, the main unit including a circuit control section for each telephone circuit, 30 a PCM conversion section having a segment coder for compressing with a ,u-LawPCM characteristic for each telephone circuit, a main control section for designating a pad multiplier which defines an attenuation value corresponding to A - 1 - ~
the employed telephone circuit, a digital sound level control apparatus for eachtelephone circuit and digital time switching means for switching speech paths, the digital sound level control apparatus comprising:
means for decompressing a received ,u-Law digital PCM signal, means for multiplying the decompressed digital signal by said designated pad multiplier, means for compressing the multiplied value to a ,u-Law PCM digital signal, and means for outputting the,u-Law digital PCM signal to the digital time switching means.
According to a second embodiment of the invention, a digital sound level control apparatus is provided for the main unit of a digital key telephonesystem, the main unit including a circuit control section for each telephone circuit, a PCM conversion section having a segment coder for compressing with a ,u-Law PCM characteristic for each telephone circuit, a main control section for designating a pad multiplier which defines an attenuation value corresponding tothe employed telephone circuit, a digital sound level control apparatus for eachtelephone circuit and digital time switching means for switching speech paths, the digital sound level control apparatus comprising:
first discrimination means for discriminating a segment region of a,u-Law PCM conversion characteristic polygonal line from a segment region signal of a PCM input data signal which is outputted from the PCM conversion section, the PCM input data including a polarity signal, a segment region signal and a step signal;
first calculation means for calculating a first level signal which is a data value before compression using the output signal of the first segment region discrimination means and the step signal of the PCM input data signal;
multiplication means for multiplying a pad multiplier by the first level signal to output a second level signal;
second segment region discrimination means for discriminating a segment region by comparing the second level signal with the coding threshold -values of segment regions based on the segment compression and decompression characteristic;
second calculation means for calculating a step signal based on the second level signal, the coding threshold signal and the intrinsic variation amount 5 per step of the segment region;
register means for forming a ~-Law PCM digital signal by combining the original polarity signal, the calculated segment region signal and the calculated step signal.
The first level signal of the digital sound level control apparatus 10 described above may be obtained by adding the product of the intrinsic variation amount per step of a segment region and the step signal to the basic normalization level signal of said segment region, or by adding the product of the intrinsic variation amount per step of a segment region and the step signal to the coding threshold value of said segment region.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:
Figure 1 is a block diagram of a monitor circuit of a conventional digital sound level control apparatus;
Figure 2 is a block diagram of an embodiment of the main unit of a key telephone system; and Figure 3 is a block diagram of pad conversion section 13 shown in Figure 2.
With reference to Figures 2 and 3, the main unit of key telephone system 1 comprises circuit control section 11, PCM conversion section 12, main control section 15, pad conversion section 13 and time divisional switch 14.
The present invention is incorporated into pad conversion section 13 and main control section 15.
Circuit control section 11 serves as an interface to telephone circuit 2 and reports to main control section 15 the classification of telephone circuits employed for incoming telephone calls. PCM conversion section 12 converts an incoming analog data signal into a ,u-Law PCM digital signal. Pad conversion section 13 outputs data signal Do which is modified from PCM input data signal ..... ,,~
-Dl from PCM conversion section 12 to digital data having a controlled sound level by decompressing, multiplying by pad multiplier Pd sent from main control section 15 and compressing to ,u-Law PCM digital data. Main control section 15 outputs multiplier Pd signal to pad conversion section 13 corresponding to the employed 5 incoming telephone circuit by discriminating by notification from circuit control section 11. Time divisional switch 14 switches telephone calls by switching the connection of the PCM highway.
PCM input data signal Dl is an 8-bit signal wherein the MSB
corresponding to the eighth bit serves as polarity signal P, the three bits 10 corresponding to the seventh to fifth bits serve as a segment region (referred to as region signal A hereafter) which identifies a segment, and the remaining fourbits corresponding to the fourth to first bits serve as step signal bits S
representative of a position in a segment.
Region signal A includes intrinsic variation signal A1 representative of 15 the variation amount per step of the level value in the segment region beforecompression, basic normalization level signal A2 (4,191 in region 8; 2,079 in region 7; 1,023 in region 6 and the like) representative of a reference point for each segment region before compression, and coding threshold value A3 (4,063 in region 8; 2,015 in region 7; 991 in region 6 and the like) representative of the 20 start point of each region before compression.
Pad conversion section 13 converts compressed PCM input data into data of the level before compression with reference to the basic normalization level signal before compression, multiplies the data of the thus converted or decompressed level by a pad multiplier to convert the data into a predetermined 25 sound volume, compresses the volume signal again, and outputs the thus compressed volume signal to the time divisional switch 14. Pad conversion section 13 includes register 31 for temporarily storing input data signal Dl, another register 32 for temporarily storing the pad multiplier signal Pd, regiondiscrimination circuit 33 for discriminating region signal A in PCM input data 30 signal Dl and dividing region signal A into intrinsic variation signal A1, normalization reference level signal A2 and coding threshold value A3, multiplication circuit 34 for multiplying step signal S in PCM input data Dl by `` 21100~1 -intrinsic variation amount signal A1, addition circuit 35 for adding basic normalization level signal A2 to the output signal of multiplication circuit 34 to output level signal Ll, another multiplication circuit 36 for multiplying input level signal Ll by pad multiplier signal Pd to produce output level signal LO, region comparison discrimination circuit 37 for comparing output level signal LO and coding threshold value A3 to determine to which region output level signal LO
corresponds, and outputting region signal A' based on the determination, subtraction circuit 38 for subtracting coding threshold value A3 intrinsic to a region determined from region signal A from output level signal LO, division circuit 39 for dividing the output of subtraction circuit 39 by intrinsic variation signal A1 to output step signal S', and register 40 for temporarily storing polarity signal P, region signal A' and step signal S'.
Operation of the embodiment will now be described below.
Analog audio data received from telephone circuit 2 are inputted by way of circuit control section 11 and converted into a PCM signal by PCM
conversion section 12. In this instance, circuit control section 11 determines whether the received call has originated from an extension line or another subscriber line and notifies the result of the determination to main control section 15.
Meanwhile, PCM coded audio data are outputted by PCM conversion section 12 to pad conversion section 13 as input data signal Dl. Separately, depending on the result of the determination of either an extension line or another subscriber line previously notified to main control section 15, pad multiplication value signal Pd representative of an attenuation amount is sent from main control section 15 to pad conversion section 13, and PCM output data signal Do for which the sound volume difference has been adjusted is outputted to time divisional switch section 14 in which a PCM highway is exchangeably connected.
The sound level difference among calls from extension lines and other subscriber lines can thus be eliminated by the way that multipliers to designateattenuation amounts are set and stored in main control section 15 in such a manner that the attenuation amount is, for example, 0 dB for a call received from outside line 2 and 6 dB for a call received from an extension line.
211~0~1 -The operation of pad conversion section 13 of the embodiment will now be described.
PCM input data signal Dl from PCM conversion section 12 is inputted to 8-bit register 31 while pad multiplier value signal Pd for determination of the 5 attenuation amount from main control section 15 is inputted to 4-bit register 32.
Region discrimination circuit 33 discriminates a region from region signal A in PCM input data signal Dl inputted to register 31 and outputs basic normalization level signal A2 intrinsic to the region, intrinsic variation amount signal A1 intrinsic to the region determined from region signal A, and coding 10 threshold value A3.
Multiplication circuit 34 multiplies intrinsic variation value signal A1 by step signal (bits 4 to 1) S of PCM input signal Dl, and the product is added to basic normalization signal A2 by addition circuit 35. The sum of the addition isoutputted as input level signal Ll. Meanwhile, polarity signal P (bit 8) of PCM
15 input data signal Dl is not inputted to region discrimination circuit 33 but is outputted as is as a polarity signal of PCM output data signal Do.
The pad multiplication value signal Pd sent from main control section 15 is inputted to and then outputted from register 32.
Multiplication circuit 36 multiplies input level signal Ll outputted from 20 addition circuit 35 by pad multiplication value signal Pd outputted from register 32 and outputs the result of the multiplication as output level LO.
Segment region comparison discrimination circuit 37, which compares coding threshold value A3 determined from region signal A by region discrimination circuit 33 and output level signal Lo outputted from multiplication 25 circuit 36, determines the region to which output level signal Lo corresponds, and outputs corresponding region signal A' (bits 7 to 5).
Further, the result of the substraction of coding threshold value A3 from output level signal LO by subtraction circuit 38 is divided by intrinsic variation signal A1 determined from region signal A' by division circuit 39, and the 30 result of the division is outputted as step signal S' (bits 4 to 1).
PCM output data signal Do after conversion into a pad value instructed by main control section 15 from polarity signal P (bit 8), region signal A' (bits 7 2110~31 -to 5), and step signal S' (bits 4 to 1) is stored once into and then outputted from register 40.
Meanwhile, main control section 15 outputs pad multiplication value Pd to pad conversion section 13 in accordance with the type of circuit. Where the 5 number of types of circuits involved is great, it may be possible to provide means for setting correspondence tables so that the corresponding pad multiplier may be outputted for each of the types of circuits.
Further, while, in the present embodiment, input level Ll is obtained by the addition of the product between intrinsic variation signal A1 and step signal 10 S to the normalization reference level signal A2, it may be obtained otherwise by the addition of the product of the intrinsic variation amount signal A1 and the step signal S to the coding threshold value A3.
As described above, since region signals and step signals corresponding to the circuits from which calls are received, rather than fixed 15 region signals and step signals, as in the case of a conventional digital sound level control apparatus, are outputted from the digital sound level control apparatus of the invention by calculating the region signal and the step signal,there is an advantage in that the reception sound level can be held substantially constant irrespective of the type of telephone circuit from which a call is received.
A
Claims (4)
1. A digital sound level control apparatus for the main unit of a digital key telephone system, said main unit including a circuit control section for each telephone circuit, a PCM conversion section having a segment coder for compressing with a µ-Law PCM characteristic for each telephone circuit, a main control section for designating a pad multiplier which defines an attenuation value corresponding to the employed telephone circuit, a digital sound level control apparatus for each telephone circuit and digital time switching means for switching speech paths, said digital sound level control apparatus comprising:
means for decompressing a received µ-Law digital PCM signal, means for multiplying said decompressed digital signal by said designated pad multiplier, means for compressing said multiplied value to a µ-Law PCM digital signal, and means for outputting said µ-Law digital PCM signal to said digital time switching means.
means for decompressing a received µ-Law digital PCM signal, means for multiplying said decompressed digital signal by said designated pad multiplier, means for compressing said multiplied value to a µ-Law PCM digital signal, and means for outputting said µ-Law digital PCM signal to said digital time switching means.
2. A digital sound level control apparatus for the main unit of a digital key telephone system, said main unit including a circuit control section for each telephone circuit, a PCM conversion section having a segment coder for compressing with a µ-Law PCM characteristic for each telephone circuit, a main control section for designating pad multipliers which defines an attenuation value corresponding to the employed telephone circuit, a digital sound level control apparatus for each telephone circuit and digital time switching means for switching speech paths, said digital sound level control apparatus comprising:
first discrimination means for discriminating a segment region of a µ-Law PCM conversion characteristic polygonal line from a segment region signal of a PCM input data signal which is outputted from said PCM conversion section, said PCM input data including a polarity signal, a segment region signal and a step signal;
first calculation means for calculating a first level signal which is a data value before compression using the output signal of said first segment region discrimination means and the step signal of the PCM input data signal;
multiplication means for multiplying a pad multiplier by said first level signal to output a second level signal;
second segment region discrimination means for discriminating a segment region by comparing the second level signal with the coding threshold values of segment regions based on the segment compression and decompression characteristic;
second calculation means for calculating a step signal based on said second level signal, the coding threshold signal and an intrinsic variation amount per step of the segment region; and register means for forming a µ-Law PCM digital signal by combining the original polarity signal, the calculated segment region signal and the calculated step signal.
first discrimination means for discriminating a segment region of a µ-Law PCM conversion characteristic polygonal line from a segment region signal of a PCM input data signal which is outputted from said PCM conversion section, said PCM input data including a polarity signal, a segment region signal and a step signal;
first calculation means for calculating a first level signal which is a data value before compression using the output signal of said first segment region discrimination means and the step signal of the PCM input data signal;
multiplication means for multiplying a pad multiplier by said first level signal to output a second level signal;
second segment region discrimination means for discriminating a segment region by comparing the second level signal with the coding threshold values of segment regions based on the segment compression and decompression characteristic;
second calculation means for calculating a step signal based on said second level signal, the coding threshold signal and an intrinsic variation amount per step of the segment region; and register means for forming a µ-Law PCM digital signal by combining the original polarity signal, the calculated segment region signal and the calculated step signal.
3. A digital sound level control apparatus as claimed in claim 2, wherein the first level signal is obtained by adding the product of the intrinsic variation amount per step of a segment region and the step signal to the basic normalization level signal of said segment region.
4. A digital sound level control apparatus as claimed in claim 2, wherein the first level signal is obtained by adding the product of the intrinsic variation amount per step of a segment region and the step signal to the coding threshold value of said segment region.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP31703092 | 1992-11-26 | ||
| JP317030/1992 | 1992-11-26 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2110031A1 CA2110031A1 (en) | 1994-05-27 |
| CA2110031C true CA2110031C (en) | 1997-04-08 |
Family
ID=18083647
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002110031A Expired - Fee Related CA2110031C (en) | 1992-11-26 | 1993-11-25 | Digital sound level control apparatus |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US5495529A (en) |
| EP (1) | EP0599653B1 (en) |
| CA (1) | CA2110031C (en) |
| DE (1) | DE69326670T2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5715309A (en) * | 1995-03-03 | 1998-02-03 | Advanced Micro Devices, Inc. | Conversion of compressed speech codes between attenuated and unattenuated formats |
| KR100520161B1 (en) * | 1998-12-30 | 2005-11-24 | 삼성전자주식회사 | Coding conversion circuit between local exchange and ISDN key phone system |
| US8804975B2 (en) | 2009-02-13 | 2014-08-12 | University Of Florida Research Foundation, Incorporated | Digital sound leveling device and method to reduce the risk of noise induced hearing loss |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3688097A (en) * | 1970-05-20 | 1972-08-29 | Bell Telephone Labor Inc | Digital attenuator for non-linear pulse code modulation signals |
| BE792988A (en) * | 1971-12-22 | 1973-04-16 | Western Electric Co | DIGITAL DEVICE |
| IT1215464B (en) * | 1987-05-07 | 1990-02-14 | Sgs Microelettronica Spa | CIRCUIT FOR THE PCM CONVERSION OF AN ANALOG SIGNAL, WITH IMPROVEMENT OF GAIN-TRACKING. |
| GB2215944B (en) * | 1987-12-28 | 1992-02-12 | Iwatsu Electric Co Ltd | Key telephone system |
| JP3085676B2 (en) * | 1989-10-30 | 2000-09-11 | 株式会社東芝 | Telephone equipment |
| CA2059883C (en) * | 1991-01-24 | 1995-08-08 | Isaku Komuro | Key telephone system provided with telephone sets connectable to add-on modules |
| US5259001A (en) * | 1991-12-17 | 1993-11-02 | Motorola, Inc. | ADPCM decoder with an integral digital receive gain and method therefor |
| JP3134455B2 (en) * | 1992-01-29 | 2001-02-13 | ソニー株式会社 | High efficiency coding apparatus and method |
-
1993
- 1993-11-24 US US08/161,928 patent/US5495529A/en not_active Expired - Fee Related
- 1993-11-25 CA CA002110031A patent/CA2110031C/en not_active Expired - Fee Related
- 1993-11-25 EP EP93309434A patent/EP0599653B1/en not_active Expired - Lifetime
- 1993-11-25 DE DE69326670T patent/DE69326670T2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0599653B1 (en) | 1999-10-06 |
| EP0599653A2 (en) | 1994-06-01 |
| US5495529A (en) | 1996-02-27 |
| EP0599653A3 (en) | 1994-12-07 |
| DE69326670T2 (en) | 2000-02-10 |
| CA2110031A1 (en) | 1994-05-27 |
| DE69326670D1 (en) | 1999-11-11 |
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| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |