US 4,288,664 AGranted

Neutralization signal developing device for an echo suppressor

AssigneeNippon Electric Co., Ltd.

InventorTakashi Araseki

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Abstract

A device for developing a neutralization signal for an echo suppressor is required for the transmission of data over a telephone line having four-wire circuits. Each transmission of data is preceded by an identification signal at a given frequency. An input analog signal including the identification is sampled and quantized so that each sampled value is encoded into a binary codeword composed of a sign bit and a preset number of bits representing the magnitude of the analog signal. The device includes a detecting circuit to detect the identification signal, a level assessing circuit to assess the level of the codeword sequence, and a hangover circuit responsive to the detecting circuit and the level assessing circuit to develop the neutralization signal. The detecting circuit includes a bit pattern generator which produces successive bit patterns from sign bits of the codeword sequence. The bit patterns are in turn used to produce a first detection signal if the bit patterns coincide with a first predetermined bit pattern and a second detection signal if the bit patterns coincide with a second predetermined bit pattern. A counter is responsive to the first and second detection signals to increase its contents by a first number of the first detection signal is generated at any one of predetermined recurrence cycles and to decrease its contents by a second number if the second detection signal is generated. The content of the counter are compared with a predetermined value, and a detection output is produced when the contents of the counter exceed the predetermined value.

Claims6

Dependent claims

A neutralization signal developing device for an echo suppressor, which is required for the transmission of data over a telephone line having four-wire circuits, each transmission of data being preceded by an identification signal at a given frequency, an input analog signal including said identification signal being sampled and quantized so that each sampled value is encoded into a binary codeword composed of a sign bit and a preset number of bits representing the magnitude of said analog signal, said device comprising:

means for receiving the series of codewords;
means responsive to a portion of each codeword in said series of codewords for detecting said identification signal;
means responsive to another portion of each codeword in said series of codewords for assessing the level of said series of codewords;
and
means responsive to the outputs of said detecting means and said level assessing means for developing a neutralization signal for the echo suppressor, wherein said detecting means includes means for successively producing bit patterns from sign bits of said series of codewords;
means responsive to said bit patterns for producing a first detection signal if one of said bit patterns coincide with a first predetermined bit pattern and producing a second detection signal if one of said bit patterns coincides with a second predetermined bit pattern;
counting means responsive to said first and second detection signals for increasing its contents by a first predetermined number if said first detection signal is generated at any one of predetermined recurrence cycles and decreasing its contents by a second predetermined number if said second detection signal is generated;
and
means responsive to the output of said counting means for producing an output signal indicating the presence of said identification signal if the output of said counting means exceeds a predetermined value.

6 more elements

A neutralization signal developing device for an echo suppressor, which is required for the transmission of data over a telephone line having four-wire circuits, each transmission of data being preceded by an identification signal at a given frequency, an input analog signal including said identification signal being sampled and quantized so that each sampled value being encoded into a binary codeword composed of a sign bit and a preset number of bits representing the magnitude of said analog signal, said device comprising:

means for receiving the series of codewords;
means responsive to a portion of each codeword in said series of codewords for detecting said identification signal;
means responsive to another portion of each codeword in said series of codewords for assessing the level of said series of codewords;
and
means responsive to the outputs of said detecting means and said level assessing means for developing a neutralization signal for the echo suppressor, wherein said detecting means includes means for dividing the recurrence cycle of sign bits of said series of codewords by a predetermined value;
means responsive to the output of said dividing means for successively producing bit patterns;
means responsive to said bit patterns for producing a first detection signal if each of said bit patterns coincides with a first predetermined bit pattern and producing a second detection signal if each of said bit patterns coincides with a second predetermined bit pattern;
counting means responsive to said first and second detection signals for increasing its contents by a first predetermined number if said first detection signal is generated at any one of predetermined recurrence cycles and decreasing its contents by a second predetermined number if said second detection signal is generated;
and
means responsive to the output of said counting means for producing an output signal indicating the presence of said identification signal if the output of said counting means exceeds a predetermined value.

7 more elements

Dependencies are inferred from the claim text.