Telephone substation apparatus for generating multifrequency signals

Claim 2

A telephone signalling arrangement comprising: a. a resonant circuit having a plurality of selectively controllable resonant frequencies; b. selector means for selecting a resonant frequency of the resonant circuit; c. amplifying means coupled to the resonant circuit for supporting oscillations at said selected frequency; d. a first switch means responsive to said selector means, which upon closure concurrently connects the parallel combination of the resonant circuit and the amplifying means to a direct current operating voltage to enable the amplifying means and to energize the resonant circuit; and a second switch means which thereafter opens to initiate oscillations in the resonant circuit which are supported by the amplyifying means.

Claim 3

A telephone subscriber arrangement for signalling a central office comprising: a. a resonant circuit including a capacitance means and an inductance means; b. selector means for selectively connecting portions of the inductance means in parallel with the capacitance means to select a desired one of a plurality of resonant frequencies; c. amplifying means coupled to said inductance means to support oscillations at said desired frequency; and d. switch means actuated by the operation of said selector means, to initially maintain the resonant circuit and the amplifying means in parallel, to subsequently connect the amplifying means and the resonant circuit to a direct current operating voltage in order to allow a direct current to simultaneously energize the amplifying means and the resonant circuit and lastly to interrupt the flow of direct current into the resonant circuit so as to initiate oscillations in the resonant circuit whereby sustained oscillations are begun at the selected frequency for transmission to the central office.

Claim 4

A telephone subscriber arrangement for signalling a central office comprising: a. a resonant circuit including a capacitance means and an inductance means; b. selector means for selectively connecting portions of the inductance means in parallel with the capacitance means to select a desired one of a plurality of resonant frequencies; c. amplifying means coupled to said inductance means to support oscillations at said desired frequency; and d. switch means actuated by the operation of said selector means, to initially maintain the resonant circuit and the amplifying means in parallel, to subsequently connect the amplifying means and the resonant circuit to a direct current operating voltage in order to allow a direct current to simultaneously energize the amplifying means and the resonant circuit and lastly to interrupt the flow of direct current into the resonant circuit so as to initiate oscillations in the resonant circuit whereby sustained oscillations are begun at the selected frequency for transmission to the central office.

Claim 5

A telephone substation circuit of a central battery type having a pair of terminals and a speech circuit of the anti-sidetone type establishing a direct current path across said terminals, said speech circuit including a voice transmitter unit and a voice receiver unit, said substation circuit further comprising: a. a multifrequency generator having a resonant circuit with discretely controllable resonant frequencies and an amplifying means; b. selector means for selecting a discrete resonant frequency of the resonant circuit, the resonant circuit being coupled to the amplifying means in such a manner as to render the amplifying means capable of supporting oscillations at said selected frequency; c. switch means, linked to said selector means, for maintaining the resonant circuit and the amplifying means in parallel prior to actuation and during the initial interval of actuation of said selector switch, for subsequently simultaneously enabling the amplifying means and the resonant circuit by connecting the amplifying means and the resonant circuit to the speech circuit so as to derive an operating voltage therefrom, and for finally interrupting the flow of direct current through the resonant circuit during the final interval of actuation of said selector switch; whereby the selected resonant frequency is generated in the resonant circuit, supported by the amplifying means, and coupled to said pair of terminals.

Claim 6

A telephone substation circuit of a central battery type having a pair of terminals and a speech circuit of the anti-sidetone type establishing a direct current path across said terminals, said speech circuit including a voice transmitter unit and a voice receiver unit, said substation circuit further comprising: a. a multifrequency generator having a resonant circuit with discretely controllable resonant frequencies and an amplifying means; b. selector means for selecting a discrete resonant frequency of the resonant circuit, the resonant circuit being coupled to the amplifying means in such a manner as to render the amplifying means capable of supporting oscillations at said selected frequency; c. switch means, linked to said selector means, for maintaining the resonant circuit and the amplifying means in parallel prior to actuation and during the initial interval of actuation of said selector switch, for subsequently simultaneously enabling the amplifying means and the resonant circuit by connecting the amplifying means and the resonant circuit to the speech circuit so as to derive an operating voltage therefrom, and for finally interrupting the flow of direct current through the resonant circuit during the final interval of actuation of said selector switch; whereby the selected resonant frequency is generated in the resonant circuit, supported by the amplifying means, and coupled to said pair of terminals.

Claim 7

A telephone substation circuit of the central battery type including a pair of terminals, an induction coil having a plurality of windings, a line impedance balancing network, a voice receiver unit and a voice transmitter unit, the voice transmitter unit being serially connected with a winding of the induction coil to form part of a series circuit establishing a direct current path across said terminals, said substation circuit further comprising: a. a multifrequency generator having a resonant circuit with discretely controllable resonant frequencies, a selector means for selecting a discrete resonant frequency and an amplifying means, said resonant circuit being coupled to said amplifying means in such manner as to render said amplifying means capable of supporting oscillations at said selected frequency; b. switch means connecting the resonant circuit and the amplifying means in parallel, said switch means responding to operation of said selector means by initially disconnecting the voice transmitter unit from said winding of the induction coil, by subsequently connecting the parallel combination of amplifying means and resonant circuit across the telephone line through said winding of the induction coil to initiate a flow of direct current through the resonant circuit and the amplifying means, and by finally interrupting the flow of direct current through the resonant circuit after said amplifying means has been enabled; whereby the selected resonant frequency is generated and coupled to said pair of terminals.

Claim 8

A telephone substation circuit of the central battery type including a pair of terminals, an induction coil having a plurality of windings, a line impedance balancing network, a voice receiver unit and a voice transmitter unit, the voice transmitter unit being serially connected with a winding of the induction coil to form part of a series circuit establishing a direct current path across said terminals, said substation circuit further comprising: a. a multifrequency generator having a resonant circuit with discretely controllable resonant frequencies, a selector means for selecting a discrete resonant frequency and an amplifying means, said resonant circuit being coupled to said amplifying means in such manner as to render said amplifying means capable of supporting oscillations at said selected frequency; b. switch means connecting the resonant circuit and the amplifying means in parallel, said switch means responding to operation of said selector means by initially disconnecting the voice transmitter unit from said winding of the induction coil, by subsequently connecting the parallel combination of amplifying means and resonant circuit across the telephone line through said winding of the induction coil to initiate a flow of direct current through the resonant circuit and the amplifying means, and by finally interrupting the flow of direct current through the resonant circuit after said amplifying means has been enabled; whereby the selected resonant frequency is generated and coupled to said pair of terminals.

Claim 9

The invention as claimed in claim 1 wherein the first and second switch means are mechanically linked to the selector means to be responsive thereto and wherein the first switch means comprises a set of early-make late-break transfer contacts and the second switch means comprises a set of later-break contacts, the later-break contacts serving to interrupt the flow of direct current through the resonant circuit so as to initiate oscillations at said selected frequency after the resonant circuit and the amplifying means have been enabled through the early-make contacts.

Claim 10

The invention as claimed in claim 3 wherein the switch means is mechanically linked to the selector means to be responsive thereto, and wherein the switch means comprises a set of early-make-late-break transfer contacts and a later-break set of contacts, the early-make contacts of said transfer contacts serving to simultaneously enable the amplifying means and the resonant circuit and the later-break contacts service to interrupt the flow of direct current through the resonant circuit so as to initiate oscillations at said selected frequency after the resonant circuit and the amplifying means have been enabled.

Claim 11

The invention as defined in claim 4 wherein the resonant circuit comprises an inductor with a plurality of tap positions and a capacitor connected to a selected one of said tap positions by the selector means, and wherein the switch means is mechanically linked to the selector means so as to operate with each operation of the selector means, the switch means having a set of early-make late-break transfer contacts and a later-break set of contacts whereby said transfer contacts, complete said series circuit in their unoperated position, and allow an operating voltage to enable the amplifying means and to energize the resonant circuit in their operated position, and whereby the later-break set of contacts interrupt the flow of direct current through the resonant circuit after said amplifying means has been enabled.

Claim 12

A circuit for a subscriber telephone set having a pair of terminals and a speech circuit of the anti-sidetone type connected across said terminals, said subscriber telephone circuit comprising: a. an induction coil with a plurality of windings, a voice receiver unit, a voice transmitter unit, and a balancing netwOrk, first, second and third windings of an induction coil and the balancing network being serially connected to establish a first direct current path across said terminals, the balancing network being interposed between the first and second windings; b. a second direct current path including the voice transmitter unit connecting the junction of the first winding of the induction coil and the balancing network to the junction of the second and third windings of the induction coil; c. a multifrequency generator having a resonant circuit with discretely controllable resonant frequencies, a selector means including a multicontact selector switch for selecting a discrete resonant frequency and an amplifying means coupled to the resonant circuit in such manner as to support oscillations at said selected frequency; d. switch means having a set of early-make-late-break transfer contacts and a set of later-break contacts, the switch means being linked to the selector switch to operate with each operation of the selector switch, the early-make transfer contacts initially closing to simultaneously enable the resonant circuit and the amplifying means by connecting the resonant circuit and the amplifying means to a voltage appearing at the junction of the first inductor winding and the balancing network, while the late-break transfer contacts, being in series with the second direct current path until operation of the selector switch, subsequently separate to interrupt the flow of direct current through the voice transmitter, and finally the later-break contacts open after the amplifying means has been enabled to interrupt the flow of direct current through the resonant circuit and initiate oscillations at said selected frequency; e. means connecting the output of said multifrequency generator to said pair of terminals.

Claim 13

A circuit for a subscriber telephone set having a pair of terminals and a speech circuit of the anti-sidetone type connected across said terminals, said subscriber telephone circuit comprising: a. an induction coil with a plurality of windings, a voice receiver unit, a voice transmitter unit, and a balancing netwOrk, first, second and third windings of an induction coil and the balancing network being serially connected to establish a first direct current path across said terminals, the balancing network being interposed between the first and second windings; b. a second direct current path including the voice transmitter unit connecting the junction of the first winding of the induction coil and the balancing network to the junction of the second and third windings of the induction coil; c. a multifrequency generator having a resonant circuit with discretely controllable resonant frequencies, a selector means including a multicontact selector switch for selecting a discrete resonant frequency and an amplifying means coupled to the resonant circuit in such manner as to support oscillations at said selected frequency; d. switch means having a set of early-make-late-break transfer contacts and a set of later-break contacts, the switch means being linked to the selector switch to operate with each operation of the selector switch, the early-make transfer contacts initially closing to simultaneously enable the resonant circuit and the amplifying means by connecting the resonant circuit and the amplifying means to a voltage appearing at the junction of the first inductor winding and the balancing network, while the late-break transfer contacts, being in series with the second direct current path until operation of the selector switch, subsequently separate to interrupt the flow of direct current through the voice transmitter, and finally the later-break contacts open after the amplifying means has been enabled to interrupt the flow of direct current through the resonant circuit and initiate oscillations at said selected frequency; e. means connecting the output of said multifrequency generator to said pair of terminals.

Claim 14

The invention as defined in claim 8 wherein the resonant circuit includes a capacitance means and an inductive means with a plurality of taps, and wherein the selector means includes a plurality of momentary contact switches arranged to connect the capacitance means across a portion of the inductive means via said taps.