US1919314A - Telephone instrument circuit - Google Patents

Telephone instrument circuit Download PDF

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Publication number
US1919314A
US1919314A US589472A US58947232A US1919314A US 1919314 A US1919314 A US 1919314A US 589472 A US589472 A US 589472A US 58947232 A US58947232 A US 58947232A US 1919314 A US1919314 A US 1919314A
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Prior art keywords
circuit
winding
impedance
line
receiver
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Expired - Lifetime
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US589472A
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English (en)
Inventor
Wigan Edmund Ramsay
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Siemens Brothers and Co Ltd
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Siemens Brothers and Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M1/00—Substation equipment, e.g. for use by subscribers
    • H04M1/58—Anti-side-tone circuits

Definitions

  • a further object of the invention is to provide an improved substation circuit having induction coilwindings anda balancing network in which two superimposed. currents may be produced in the receiver circuit by the operation of the transmitter in case of an unbalanced condition" between the-line and time is connected to the substation circuit.
  • Fig. "1' shows the relation between the voltage applied at the microphone terminals and the current generated in the receiver'circuit for a particular circuit ata frequency of Fig. shows the loci of the points P and Qtaken'from'Fig. 1 as the frequency is varied for a particular-circuit. 1
  • Fig. 3 show'stlie effect on the locus'of Q when the characteristics of thedifferent parts of the circuit are varied.
  • the loci shown in Fig. 4 represent the movement of the head o-f the impedance Vector in different cases in practiceat varying frequencies.
  • v p v Figs. 5, 6,' and 7 show three differentsubstation or instrument circuits having their in-- in different ways.
  • i 3 a The twoloci shown in 8 and 9 show the effect of the difference between two circuits.
  • I L W Fig. '10 shows asubstation'circuit andconnections in a desk instrument for anauto matic, telephone system. i I
  • Fig. 11 shows a substation circuit and connections wherein'a resistance -'-and a con-v denser is used to form'a spark quenching circuit for the dial impulse springs.
  • circuits are1proposed involving a three winding'induction coil and a balancingnetwork, the receiver circuit being shunted across a part of the.
  • balancing network and the transmitter being shunted across a part of the network containing a winding of the induction coil and a condenser in series.
  • the receiver and the third winding. of the induction coil are tapped off the whole or a part ofthe impedance in thebalancing network.
  • the transmitter feedcurrent from the line flows through the winding L2 of the induction coil and the transmitter T.
  • the current passing through the winding L2 induces a current flow in the winding L3 which actuates the receiver R. 7
  • an E. M. F. from the primary circuit is produced. in the receiver circuit.
  • the induced E. M. F. and the'E. M. F. from the primary circuit may oppose or aid each other dependent upon the connection of the terminals of the receiver circuit across the impedance Z.
  • the characterlstics of the circuit shown in Fig. 6 are substantially the same as that shown in Fig. 5.
  • induction coil is connected in series with the impedance Z and then bridged across the receiver circuit including the receiver R and Winding L3.
  • v The characteristics of the circuit shown in Fig. 7 are substantially the same as, that shown in Fig. 5.
  • the induction coil'winding L1 in this case has been reversed with respect to the winding L2 and the winding L1 is now' included in the transmission bridge including the transmitter T and winding L2.
  • I have investigated mathematically the variation of side tone with line impedance where i is the side tone current due to a voltage e enerated'in the microphone when the 'lineimpedanceis equal to Z;;+AL.
  • the L1 windingof the Z is that value of line impedance which gives zero side tone at the frequency considered.
  • AL is the vector difierence between Z
  • Z0 is the impedance of the instrument circult measured. from the hue terminals with the microphone and receiver connected.
  • PLa is a voltage step up ratio equal to the ratio of the open circuit a. c. voltage at the line terminals to an E. M. F. applied at the microphone ter1ninals.- v
  • KL 0 is the current step-downratio, equal to the ratio of the receiver current to the incoming line current.
  • Z0, PL a and KL@ can be ascertained by measuring methods in a particular instrument.
  • the equation shows that the side tone current is related as follows: (1) to the product of the transmission and reception eificiency.
  • the transmission efiiciency is proportional to I I Pia (Zcv Z AL) and the reception efiiciency to K40 (Z0 ZL AL) line impedance result in relatively large changes in side tone.
  • Fig. 1 should be referred to which depicts I a particular case experimentally confirmed) at a particular frequency of 796 cycles per second.
  • Values along the abscissa axis from the point O represent resistance component values of line impedance.
  • the values along 7 the ordinate axis through 0 represent reactance component values of the line impedance. Positive values are above the abscissa' axis, negative below. The value. of
  • Z0 for the instrument circuit is given by P0 and 0Q represents the line impedance for which the side tone is zero.
  • the impedance is represented'by the point'R, the impedance being OR then AL is represented by the line QR and the ratio AL (Zc+Z AL) is given by the ratio of QR to PR.
  • the locus of R is a circle although the circle may have infinite diameter as evidenced by the line locus AA which is at right angles to the line PQ. Any particular locus shows how AL may vary whilstthe side tone current remains constant although altering in phase.
  • the values such as0.2 m. a/V indicate for the particular circuit considered the receiver current is 0.2 millianiperes per volt a. c. generated at the microphone. A value. of 0.5 appears to be tolerable. A value over 0.6 becomes annoying and'a value below 0.2 gives a sensation of deafness to the user.
  • a 600 ohm non-reactive junction line connected to the instrument through a stone bridge would provide a line impedance of 600-1200 ohms approximately.
  • the side tone ratio with zero local. line resistance would be about 0.1 In. a./V.
  • Vith 450 ohm local line the side tone ratio would be about 0.2 m. a. /Vall taken at 796 cycles per second.
  • Figs. 5, 6 and 7 represent three ment circuits included in the present invention.
  • the receiver is designated R
  • the transmitter by T
  • the line terminals are denoted by L
  • C is a condenser
  • Ry is a resistance
  • Z an impedance.
  • the bell is omitted but would be as is usual Connected between one line branch and the con denser, the condenser being a necessity in the case of common battery working.
  • the induction coil has three windin s de-' noted L1, L2, L3.
  • the letters 8 and f e note the start and finish of windings. and finish of coil L3 is not shown for a reason which will later appear. being wound in the same direction'round the core the terms start and'finish have the well understood meanings.
  • the impedance Z, resistance By and condenser C is a unit which playsa major part in determining the Z value of the instrument circuit. 'R'y and Z maybe tapped'so that L3 andthe receiver R'may be shunted across a part or the whole of the series connection of the two.
  • Locus D may be obtained by using a winding L3 of comparatively low inductance.
  • the locus C may be obtained by reversing the connection of winding L3 that is by connecting its finish end to f of winding L1.
  • Loci which cross over the resistance axis such as E and F are produced when the impedance Z contains inductance orcapacity.
  • locus F Ry is comparatively large.
  • the single point G results from a condenser and resistance of special values in the balancing part.
  • the locus H is produced in cases in which there appreciable leakage inductance in the induction coil windings and is a modification of the locus D.
  • the locus H has certain advantages- Clearly by suitable design of the instrument circuit the movement of Q in Fig. 1 when the frequency changes may be varied considerably and offers the possibility of suiting the instrument to lines on which it may be used.
  • Fig. 4 shows graphs of cases which occur in practice.
  • a locus here such as L shows the movement of the head of an impedance vector with frequency.
  • the points which .are encircled refer as in Fig. Q'to frequencies of 500-, 796, 1592 and 3184 cycles per second.
  • the impedance vector of course, has one end at O and its head on a locus.
  • the locus J is the locus of the head of the impedance vector for a long'length of standard cable in series with a 150 ohm local line.
  • the locus K represents the same circuit in whiehhowever is included a stone feeding bridge with 'a 2 m.f. condenser in each Wire.
  • LocusL refers to a long junction line of 150 lb; aerial wire with a local line of 150 ohms.
  • Locus M refers to a case in which the impedance which faces the instrument is that of a non-junction connection between two subscribers using similar instrument circuits on the same automatic exchange the local line resistance being assumed to be 150 ohms to each instrument.
  • windings L1 and L2 are connected as an auto-transformer giving a step up of voltage fromthe microphone to the line.
  • the size of the winding LS' hasan effect on the shape of the Q locus but may be arranged to give good reception efficiency.
  • lVindings L1 and L2 in Figs. 6 and 7 act also as step uptransformers L2 in Fig. 7 having more turns than L1.
  • the plus or minus signs are used according to the connection of the receiver winding L3.
  • the upper sign is used when the finish of L3 is connected to the receiver and the lower (minus) sign when itis the start that is connected to the receiver.
  • Equation (5) the numerator and denominator can each represent an impedance equivalent to a condenser and a resistance in series.
  • Such a circuit arrangement can be adjusted in such a wa that the impedance ZL is independent of requency, that is, be: comes a pure resistance.
  • the arrangement is then aperiodic.
  • Each Equation -1, 2 and 3 allows of an aperiodic arrangement.
  • thelower sign of the two alternative signs is used.
  • thelower sign is used f T1 is less than unity and the upper sign 1f T1 is greater than unity.
  • Equation (1) If ZL is to be independent of frequency the numerator anddenominator of the fraction must have the same angular value at all frequencies. v
  • Equatmg tangent values This value of th Fig. 3.
  • ZL gives the locusG in
  • the resistances of the induction coilwind-- ings are not'taken account of in the equations Ry, Z and C are the elements before men 7 for the reason that they are designedly low and although they may rise with frequency do not disturb the equations to an extent greatly influencing design.
  • I The effect of leakage inductance is to add to ZL a negative rcactance equal to the positive reactance of the leakage' inductance at each frequency.
  • the sign of connection of receiver winding is positive. 7 v
  • the induction coil, windings may have a d. c. resistance of about 20 ohms each.
  • the locus of Q is shown'in Fig. 8- for this case.
  • the locus'marked K gives thempedance locus of a circuit of the same im pedance (e.g. a distant twin instrument) measured with .150' ohms in series, andseen through a Stone bridge with 150 ohms on the outgoing side.
  • the two loci overlap but there is no great divergence at the main speech frequencies.
  • the sign of connectionof the receiver winding is negative.
  • the locus of Q here isofthe form marked H in Fig. 3. This may be comparediwith the locus J of Fig. 4 which concerns a cable standard 20 lb. wire asmeasured from the end of. a ohm loop through a repeating coil exchange circuit. The two' loci are shown in Fig. 9. The inflexion in the locus H is due to leakage inductance in the induction coil. a f
  • The. circuit is; as in Fig. 5 and the sign of connection of the receiver winding is positive. 1
  • the receiver impedance was 124+j .230 ohms-at 7 96 c. p. a.
  • the transmitter had a resistance of the order of 50 ohms and the induction coil windings had an a. c. resistance of the order of 20 ohms.
  • the resistance Ry may however be included in the Winding of L1 in the cases of Fig. 5 by winding the coil with a high resistance alloyor'with-small gauge copper the case of Fig. 6. o v p
  • Both resistance Ry and impedance Z may be tapped so that bothmay' be adjusted. to
  • Resistance in Z may go in coil'Ll in suit the'line with which the instrument may be used.
  • DL is the dial and DLa and DLb are dial off-nor- -mal contacts. Switch hook. contacts are situated at X and are closed when the instrument is taken into use. j 7
  • the resistance Ry is formed by the high resistance winding L1.
  • the impedance Z may be resistance or resistance and reactance.
  • Thefresistance (Ry) may however be associated with the condenser in the bell box and if desired may be included so as to be in series with the bell or condenser
  • the talking circuits of Fig. 10 are substantially the same as those described for Fig. 5 and therefore need not be described in detail.
  • Fi 11 shows a case in which the resistance Iiy is used in conjunction with the condenser C to form a spark quench for the dial impulse contacts.
  • the talking circuits of Fig. 11 are somewhat similar to those described for Fig.5.
  • the dial off normal springs DLa and DLZ close to provide the impulse circuit which may be traced as follows: from the upper line L, impulse springs DL, oil normal springs DLa and DLZ), the lower switchhook springs X and to the lower line L.
  • the circuit for quenching the spark at the impulse springsDL may be traced from springs DL, condenser C, resistance By, and off normal springs DLa .back to the impulse springs DL.
  • a substation telephone circuit comprising a transmitter, a receiver, two imp'edances connected in series, an induction coil having three windings, a line, a series circuit including the second of said windings and said transmitter in series connected in bridge of said line, a second series circuit including said two impedances-and the first of saidwindings in series connected in bridge of said transmitter, and circuit means connecting the third of said windings in series with said receiver across one of said impedances.
  • a substation telephone circuit prising a transmitter, a receiver, two impedances connected in series, an induction coil having three windings, aline, a series circuit including the second. of said windings and said transmitter in series connected in bridge of said line, a second series circuit including said two impedances and the first of said windings in series connected in bridge of said transmitter, and circuit means for connecting the third of said windings in series with said receiver in bridge of that portion of said second series circuit including one of said impedances and said first wmding.
  • a substation telephone circuit comprising a transmitter, a receiver, two impedances connected in series, an induction coil having three windings, a line, a series circuit including the first and second of said windings and said transmitter in series connected in bridge of said. line circuit, a second series circuit including. said two impedances in series connected in bridge of that portion of said first series circuit including said first winding and said transmitter, and circuit means connecting the third of said windings in series. with said receiver across one of said impedancesf 3 i 7 4.
  • a transmitter comprising a transmitter, a receiver, a first impedance including a resistance and a condenser in series, a second impedance connected inseri es with said first impedance, an induction coil having three windings, a line, an impulse transmitting device for transmitting impulses over said line, a first series circuit including the second of said windings and said trans-,
  • a balancing network for side tone reduc- CJI tion including two impedances and another winding of the induction coil in series bridged acrosssaid transmitter, and a receiver circuit including a receiver and a third winding of the induction coil in series connected in a bridge of one of said impedances.
  • a trans mitter circuit including a transmitter and one winding of an induction coil, a balancing network for side tone reduction including two impedances and another winding of the induction coil in series connected in bridge of said transmitter, a receiver circuit including a receiver and a third winding of the induction coil connected in bridge of one of said impedances, means including said windings and connections responsive to the operation of said transmitter during speech transmission for causing two superimposed currents to flow in said receiver circuit.
  • a transmitter circuit including a transmitter and one winding of an induction coil, a balancing network for side tone reduction including two impedances and another winding of the induction coil in series connected in bridge of said transmitter.
  • a receiver circuit including a receiver and a third winding of the induction coil connected in bridge ofone of said impedances, means including said windings and connections responsive to the operation of said transmitter during speech transmission for causing two superimposed currents to flow in said receiver circuit, said superimposed currents assisting or opposing each other dependent upon the connection of the receiver circuit to said one impedance.
  • a substation telephone circuit comprising a transmitter circuit including a transmitter and one winding of an induction coil, a balancing network for side tonereduction including another winding of the induction coil, an impedance, a pure resistance, and a condenser in series connected in bridge of said transmitter. and a receiver circuit including a receiver and a third winding of r the induction coil 111 series connected in bridge of said impedance.
  • a substation telephone circuit comprising a transmitter circuit including a transmitter and one winding of an induc- .tion coil in series, a balancing network for side tone reduction including another wind ing of the induction coil, a first nure resist-- v ance, a second pure resistance. and a condenser in series connected in bridge of said transmitter, and a receiver circuit including a receiver and a third winding of the induction coil in series connected in bridge of said first resistance.
  • a substation telephone circuit comprising a transmitter circuit including a transmitter and one winding of an induction coil in's'eries, a balancing network for side tone reduction including another winding of the induction coil, an impedance, a tapped resistance, and a condenser in series connected in bridge of said transmitter, and a receiver circuit including a receiver and a third winding of the induction coil in series connected in bridge of saidimpedance.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Details Of Connecting Devices For Male And Female Coupling (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)
  • Springs (AREA)
US589472A 1931-02-07 1932-01-28 Telephone instrument circuit Expired - Lifetime US1919314A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB3949/31A GB372400A (en) 1931-02-07 1931-02-07 Improvements relating to telephone instrument circuits
GB3238/34A GB425566A (en) 1931-02-07 1934-01-31 Improvements in or relating to telephone instrument circuits

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US1919314A true US1919314A (en) 1933-07-25

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US589472A Expired - Lifetime US1919314A (en) 1931-02-07 1932-01-28 Telephone instrument circuit
US1318A Expired - Lifetime US2099381A (en) 1931-02-07 1935-01-11 Telephone instrument circuit

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Application Number Title Priority Date Filing Date
US1318A Expired - Lifetime US2099381A (en) 1931-02-07 1935-01-11 Telephone instrument circuit

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US (2) US1919314A (ja)
BE (1) BE386269A (ja)
FR (1) FR732067A (ja)
GB (3) GB372400A (ja)
NL (1) NL35830C (ja)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2524350A (en) * 1945-07-13 1950-10-03 Kellogg Switchboard & Supply Telephone set with means for adjusting its antisidetone circuit
US2912512A (en) * 1956-06-19 1959-11-10 Gen Telephone Lab Inc Anti-sidetone and line balancing telephone circuit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2417067A (en) * 1947-03-11 Telephone substation circuit

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2524350A (en) * 1945-07-13 1950-10-03 Kellogg Switchboard & Supply Telephone set with means for adjusting its antisidetone circuit
US2548723A (en) * 1945-07-13 1951-04-10 Kellogg Switchboard & Supply Telephone set hook-switch apparatus
US2912512A (en) * 1956-06-19 1959-11-10 Gen Telephone Lab Inc Anti-sidetone and line balancing telephone circuit

Also Published As

Publication number Publication date
US2099381A (en) 1937-11-16
GB425566A (en) 1935-03-18
BE386269A (ja) 1932-03-31
GB372400A (en) 1932-05-09
GB407808A (en) 1934-03-29
FR732067A (fr) 1932-09-13
NL35830C (ja) 1935-07-15

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