EP0147791A2
Expired / Lapsed
EP
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Dual-tone multiple-frequency-signal generating apparatus
Assignee: Toshiba Corp
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Filing: 1984-12-19
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Granted: —
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Expires: 2004-12-19
Abstract
Abstract A dual-tone multiple-frequency (DTMF)-signal generating apparatus of the present invention is provided with a high-group frequency divider (13) and a low-group frequency divider (14) for dividing a reference frequency signal into high-group frequencies and low-group frequencies, respectively. The respective outputs from the high-group divider (16) and the low-group divider (17) are supplied to a high-group-sine-wave-signal generator (16) and a low-group-sine-wave-signal generator (17). The high- and low-group-sine-wave-signal generators (16, 17) comprise a plurality of bi-stable circuits (D, through D 18 ) and include shift registers (28, 38) for sequentially shifting a divided input signal within a predetermined period, a plurality of switches (S 1 through S 18 ) which selectively pass high or low level signal corresponding to the outputs of the respective bi-stable circuits, and a plurality of capacitive elements (C 1 through C 18 ) in which the terminals on one side thereof are supplied with the high or low level passed by the plurality of switches, and the terminals on the other side thereof are commonly connected, the high or low level being applied to the common connection for every cycle of the shift registers to produce the high- and low-group-sine-wave signals from the common connection. The respective sine wave signals are level converting by a high-group level converter comprising a capacitor (C H1 ) and a switch (42) and by a low-group level converter comprising a capacitor (C H2 ) and a switch (46). The level converted high- and low-group-sine-wave signals are combined by a mixer (53) comprising buffer amplifiers (OP 1 , OP 2 ), resistors (R,, R 2 ) and a transistor (Tr,), thereby obtaining a DTMF signal.
Inventors
- 👤 Eiji C/O Patent Division Masuda
- 👤 Yasuhiko C/O Patent Division Fujita
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-03 21:06
CPC Classifications
H; H04; H04M; H04M1/00; H04M1/26; H04M1/30; H04M1/50; H04M1/505
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
206 words
A dual-tone multiple-frequency-signal generating means including frequency dividing and sine-wave-signal generating means for dividing a reference frequency signal from a reference-frequency-signal generator (11) into first and second divided frequencies and for generating first and second sine wave signals having approximately the same cycles as those of first and second standard frequencies using the first and second divided frequencies, and mixing means for combining the first and second sine wave signals output from said sine-wave-signal generating means (16, 17) and for sending the combined signal to a telephone communication line as a dual-tone multiple frequency signal characterized in that said mixing means comprises: first level converting means (C H1 , C H2 , 42) with high input impedance for receiving and level converting the first sine wave signal; second level converting means (CL 1 , C L2 , 46) with high input impedance for receiving and level converting the second sine wave signal; and combining means (OP 1 , OP 2 , R 1 , R 2 , Tr l ) connected to said first and second level converting means for combining the first and second level converting sine wave signals output from said first and second level converting means to produce the dual-tone multiple frequency signal.
Claim 2
Dependent Claim
206 words
A dual-tone multiple-frequency-signal generating means including frequency dividing and sine-wave-signal generating means for dividing a reference frequency signal from a reference-frequency-signal generator (11) into first and second divided frequencies and for generating first and second sine wave signals having approximately the same cycles as those of first and second standard frequencies using the first and second divided frequencies, and mixing means for combining the first and second sine wave signals output from said sine-wave-signal generating means (16, 17) and for sending the combined signal to a telephone communication line as a dual-tone multiple frequency signal characterized in that said mixing means comprises: first level converting means (C H1 , C H2 , 42) with high input impedance for receiving and level converting the first sine wave signal; second level converting means (CL 1 , C L2 , 46) with high input impedance for receiving and level converting the second sine wave signal; and combining means (OP 1 , OP 2 , R 1 , R 2 , Tr l ) connected to said first and second level converting means for combining the first and second level converting sine wave signals output from said first and second level converting means to produce the dual-tone multiple frequency signal.
Claim 3
Dependent Claim
88 words
An apparatus according to claim 1, characterized in that said first level converting means (CH 1 , CH 2 , 42) comprises: first and second serially connected capacitors (C R1 , C H2 ) in which the terminal on one side of the capacitors is supplied with the first sine wave signal and the terminal on the other side thereof is grounded; and a switch circuit (42) with one terminal connected to a reference voltage and other terminal connected to a connection of said first and second capacitors.
Claim 4
Dependent Claim
82 words
An apparatus according to claim 1, characterized in that said second level converting means (C L1 , C L2 , 46) comprises: first and second serially connected capacitors in which the terminal on one side of the capacitors is supplied with the second sine wave signal and the terminal on the other side thereof is grounded; and a switch circuit (46) with one terminal connected to a reference voltage and other terminals connected to a connection of said first and second capacitors.
Claim 5
Dependent Claim
228 words
An apparatus according to claim 1, characterized in that said first and second level converting means (C H1 , C H2 , 4 2, C L1 , C L2 , 46) comprise: first and second serially connected capacitors (C H1 , C H2 , C L1 , C L2 ) in which the terminals on one side of the capacitors are supplied with the first and second sine wave signals, respectively, and the terminals on the other side thereof are grounded; and switch circuits (42, 46) with the terminals on one side of the switch circuits connected to a reference voltage and the terminals on the other side thereof connected to a connection of said first and second capacitors, and that said mixing means (OP 1 , OP 2 , Ri, R 2 , Tr l ) comprises: first and second buffer amplifiers (OP 1 , OP 2 ) connected to the connection of said first and second capacitors for performing an impedance conversion; first and second serially connected resistors (R 1 , R 2 ) with the terminals on one side of the resistors connected to the outputs of said first and second buffer amplifiers and the terminals on the other side thereof are commonly connected; and a transistor ( Tr l ) whose base is connected to the common connection of said first and second resistors.
Claim 6
Dependent Claim
51 words
An apparatus according to claim 4, characterized in that said first and second buffer amplifiers (OP 1 , OP 2 ) comprise operational amplifiers whose positive input terminals are connected to the connection of said first and second capacitors and whose negative input terminals are connected to the output terminals thereof.
Claim 7
Dependent Claim
159 words
An apparatus according to claim 1, characterized in that each of said first and second level converting means (C H1 , C H2 , 42, C L1 , C L2 , 46) comprises: first and second serially connected capacitors with the terminals on one side of the capacitors supplied with the first and second sine wave signals; and switch circuits (42, 46) with the terminals on one side thereof connected to a reference voltage and the terminals on the other side thereof connected to the connection of said first and second capacitors, and that said mixing means comprises: first and second MOS transistors (Q 3 , Q 4 , Q 5 , Q 6 ) in which a gate of one MOS transistor is connected to the connection of said first and second capacitors to form a source follower; and output resistors (R 1 , R 2 ) connected to the serial connection of said first and second transistors.
Claim 8
Dependent Claim
84 words
An apparatus according to claim 1, characterized in that said first and second level converting means and said mixing means comprise: first and second MOS transistors (Q 7 , Q 8 ) whose sources are commonly connected and serve as source coupled pairs; and - a third MOS transistor (Qg) whose drain is connected to the common connection of sources of said first and second MOS transistors and serves as a load, the source combined voltage being produced as a dual-tone multiple frequency signal.
Claim 9
Dependent Claim
76 words
An apparatus according to claim 1, characterized in that said first and second level converting means and said mixing means comprise: first and second integrators (61, 62); first and second switch circuits connected to said first and second integrators in parallel, respectively; and an operational amplifier (63) connected to the common connection of said first and second integrators for producing a combined output signal from said first and second integrators as a dual-tone multiple frequency signal.
Claim 10
Dependent Claim
108 words
An apparatus according to claim 1, characterized in that said first and second level converting means and said mixing means comprise: first and second source follower circuits (66, 67) whose outputs are commonly connected through a resistor so as to receive the first and second sine wave signals and to produce the combined signal; operational amplifiers (OP 7 ) whose positive input terminals are supplied with a combined signal of the first and second sine wave signals and whose negative input terminals are supplied with a reference voltage through a third source follower circuit; and a transistor (Tr 4 ) connected to the output of said operational amplifiers.
Claim 11
Dependent Claim
29 words
An apparatus according to claim 9, characterized in that the output of the operational amplifier ( OP7 ) is fed back to its negative input terminal through a resistor.
Claim 12
Dependent Claim
108 words
An apparatus according to claim 1, characterized in that-said first and second level converting means and said mixing means comprise: first and second source follower circuits (66, 67) whose outputs are commonly connected through a resistor so as to receive the first and second sine wave signals and to produce the combined signal; operational amplifiers (OP 8 ) whose negative input terminal is supplied with a combined signal of the first and second sine wave signals and whose positive input terminal is supplied with a reference voltage through a third source follower circuit (69); and a transistor (Tr 4 ) connected to the output of said operational amplifiers.
Claim 13
Dependent Claim
29 words
An apparatus according to claim 11, characterized in that the output of the operational amplifier (OO 8 ) is fed back to its negative input terminal through a resistor.
Claim 14
Dependent Claim
170 words
An apparatus according to claim 1, characterized in that said sine-wave-signal generating means (16, 17) comprises: shifting means which comprises a plurality of bi-stable circuits and which sequentially shifts the divided frequency signal from said frequency dividing means within predetermined periods; a plurality of switches (S 1 through S 18 and S 1 through S 16 ) for selectively passing the first and second voltage levels, which are different than each other, corresponding to the outputs of the respective bi-stable circuits in said shifting means; and a plurality of capacitive elements (C l through C 18 and C 1 through C 16 ) in which the terminals on one side of the capacitive elements are supplied with the first or second voltage level passed by the plurality of switches and the terminals on the other side thereof are commonly connected, the first or second voltage level being applied to the common connection for every cycle of said shifting means to produce sine wave signals from the plurality of common connections.
Claim 15
Dependent Claim
40 words
An apparatus according to claim 1, characterized in that said reference-frequency-signal generating means (11) includes a MOS device (llf) and a natural frequency element (llc) and for generating a reference frequency signal having an oscillating frequency of approximately 480 KHz.
Claim 16
Independent Claim
70 words
An apparatus according to claims 1 through 12, characterized by further comprising keyboard interface means (12), connected to said key input means (15) and said frequency dividing means (13, 14), for supplying to said frequency dividing means division ratios for achieving the said first and second divided frequencies using the reference frequency signal from the reference-frequency-signal generating means (11), corresponding to a key actuated in said key input means (15).
References Cited (Backward Citations)
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