US1616193A - Selective signaling circuits - Google Patents

Selective signaling circuits Download PDF

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Publication number
US1616193A
US1616193A US740528A US74052824A US1616193A US 1616193 A US1616193 A US 1616193A US 740528 A US740528 A US 740528A US 74052824 A US74052824 A US 74052824A US 1616193 A US1616193 A US 1616193A
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Prior art keywords
filter
filters
frequency
transmission
impedance
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US740528A
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English (en)
Inventor
Ralph H Mills
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AT&T Corp
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Western Electric Co Inc
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Priority to US740528A priority Critical patent/US1616193A/en
Priority to FR593368D priority patent/FR593368A/fr
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J1/00—Frequency-division multiplex systems
    • H04J1/02—Details
    • H04J1/04—Frequency-transposition arrangements
    • H04J1/045—Filters applied to frequency transposition

Definitions

  • 'lihis invention relates to selective signaling circuits such as are used, for example,
  • An object of the invention is to improve ,the transmission of such a selective signaling circuit.
  • the several trans- 20 ⁇ mitting .band filters in a given system have their end sections all ⁇ connected in series with each other Vand the common transmission circuit.
  • the several receiving band filters have their end sections connected ink series with each other and with the common receiving cfrcuit.
  • the common transmitting and common receiving circuits are then connected to' a common transmission line by means of a hybrid coil and balancing network.
  • the transmission characteristics of the loW- est and highest of a group of filters operating 4either in parallel or in series are im- ⁇ proved by means of lsimulating networks. which have the same react-ance as an additional adjacent ⁇ filter would have 'at the desired cut-ofil frequency.
  • Fig. l is a diagrammatic illustration of one terminal of a multiplex carrier current ln other known types of carrier Wave' telephone system embodying the invention.
  • Fig. 3 showscurvesillustrating theI impedance characteristics of these filters.
  • F ig. 4 shows a modification of the system of Fig. l.
  • the carrier terminalapparatus shown in Fig. l comprises a plurality of two-way carrier Wave signaling channels I', II and III, each having a1 transmitting and a receiving branch. 4
  • FElie transmitting branches of these chan'- nels are connected in parallel to the transf mission line ML through a common transniitting circuit TL, and the receiving branches vare connected'in parallel to the iie ML through a common receiving circuit
  • Transmissions in the several two-way channels I, l1 and H1 are eected by cari and .higlrpassv filters LP and HP are asso-v ciated with the common transmitting and receiving circuits TL and RL, respectively;
  • filters may be of the type diselosed'in the United States patent to G. A. Campbell, No. 1,227,113, issued May 22, 1917.
  • the two-way carrier wave signaling channel I has in its transmitting branch a transmitting oscillator T01, a modulator M1 and a transmitting band filter vTBFl.
  • the receiving branch of the' carrier wave signaling channel I includes a receiving band filter RBF1, a detector and amplifier DA1, a receiving oscillator B01 and a voice frequency filter F1.
  • a low frequency line L1 whichmay be an ordinary subscribers telephone circuit, is
  • the voice frequenc filter F1 maybe of the ordinary low pass lter type disclosed in the Campbell patent, supra, and is designed to transmit to the low frequency line L1 currents of voice frequencies appearing in the output. of the demodulator and'amplifier DA1 and to suppress from transmission the higher frequency components of demodulation.
  • the transmitting band filter TBF1 and the receiving band filter BBF1 may be of the composite wave filter type discussed in part 3. of an article on the Theory and design of uniform and composite electric wave-)- filters, by O. J. Zobel in the Bell System Technical Journal of January, 1923. i
  • These filters consist, in general, of a plurality of sections having'series and shunt reactances designed, according to well known laws, to
  • the carrier system outlined above is of the type in which the carrier wave of each channel is suppressed from transmission -when no signals are being transmitted, and
  • Transmitting band filters TBF1, TBF2 and TBF3 are designed to transmit respective bands of frequencies comprised within the lowerl group in an ascending frequency scale. The frequencies comprised within this lower group are transmitted to the line ML through the low pass filter LP.
  • the receiving band filters RBF1, .RBFl and HBF3 are designed to transmit respective bands of frequencies comprised within the upper group in the frequency scale which are transmitted thereto by the high pass filter Hl), a certain particular band of these frequencies being diverted into filter RBF1, another particular band into RBF2 and another into RBF3. These three bands of frequencies originated at the other or distant end of the line ML. l
  • the fractional terininations are' so proportioned that for the free transmitting range of each filter the remaining filter or lters operate to reduce impedance lirregularities of 4each filter.
  • a particular advantage of this arrangement is that the reactance annulling effect ⁇ of each filter on either side of a given filter in the' frequency .displacement scale tends to improve the transmission loss characteristic of the given lter at and in the vicinity amp1e,.sinc ⁇ e transmitting band filters TBFl, TBFZ'and TBF3 are all connected in parallel to the common transmitting circuit TL, 'the transmission loss characteristic of filter TBF? is improved in the neighborhood of its lower cut-off frequency by the presence of filter TBFl and near its'upper cut-off frequency bythe presence of filter TBFS.
  • Fig. 3A illustrates the impedance characteristicsof band filters TBF ⁇ TBF2 and- TBFS, as well as the supposititious impedance characteristics of the fictitious band filters A and B.
  • the impedance characteristics ,of the fictitious' band filters A and B indicated by the dotted curves of Fig.l 3 may, o course, be readilydetermined since these filters would be designed to transmit a Well-defined range of frequencies if they were' actually included in the frequency l scale.
  • the network which is to ⁇ be inserted in parallel with the filter TBI"1 will only be required vto simulate thei'mpedancek of the ⁇ fictitious filter A ⁇ through a small range of transmission.
  • the :impedance of the fictitious filter A at the frequency ff comprises .simply the' positive reactance -l-a, as indicated by the dotted ordinate of Fig. 3.
  • the reactance +008 may be vonlyanl inductance coil since an inductance coil has a positive reactance.
  • ⁇ the value of the simu ating network may be computed from the J formulae given below provided the other elements in circuit with the filterwhose cut-off 1s to bev improved ⁇ are fixed impedances.
  • the transmission lcharacteristic of the filter 'IBF3 may likewise be improved 1n ing band filters work SN3, designed to improve the neighborhood of its upper cut-ofi' frequency ff by inserting in parallel therewith a network which simulates at this particular frequency the impedance of the fictitious filter B whose Vtransmission band lies in the frequency scale just above that of filter TBF3.
  • the impedance of the fictitious lter B is simply a ne ative reactance as indicated by the otted ordinate of Fig. 3. Since the reactance -b has a negative value it may be represented in its simplest case b a condenser, the capacit of which may e determined from the fol owing formula:
  • w is the known reactance of fictitious filter B at any frequency f and c is the resulting capacity of the condenser in farads.
  • frequency f3 may be represented as:
  • these filters are esigned to transmit predetermined bands of frequencies in an ascending frequency scale, and accordingly the curvesl of Figs. v2 and 3 which have been used in connection with the description of filters TBF1, TBFs and TBFS, also apply in every particular to the receiv- RBF1, BBF2 and RBFG.
  • the simulating netthe transmission characteristic of filter R-BF1 at its lower cnt-off and the simulating network SN4 designed to improve the transmission frequencies and impedanf'es -of the trans mining bandl filters.
  • l Fior. 4 shows a modification of the inven? tion 1n which the various transmitting and receiving band filters are connected in series with the transmission line instead of in parallel as has been assumed heretofore. lin this case, the transmission characteristics of transmitting band.
  • filters TBF1 and TBF characteristics of filters TBF1 and TBF3 are indicated schematically at TFN and thetwo networks designed to improve the transmislsion characteristics of filters RBF1 and HBFa are indicated schematically at RFN.. .j
  • the impedance characteristics of a group of band filters connected in series is; however,
  • impedance of a fictitious filter A at the lower cut-ofi' frequency .fx1 ofthe .filter TBFl of Fig- 4 instead/of being a positive reac# tance is a negative reactance and'accordlngly in its simplest case the network simulating such a reactance would be a condenser instead of an inductance coil.
  • the impedance of a fictitious filter B at the cutoff frequency faz of the filter TBF3 of Fig. 4 is a positive reactance instead 'of a negative reactancc, and accordingly in its simplest case theI network simulating this reactance would be an inductance coil.
  • the same conditions also ap ly to the receiving band filters RBF1 and BF3 of Fig. 4.
  • each adjacent lter have the effect of reducing the transmission loss of any filter in the neighborhoodof the cut-off frequency, but they also increase the loss in the at-tenuating regions of the given filter where, of course,
  • the invention 'ma' be employed to adters TBF1 and TBF.3 in the usual manner.
  • filter TBF1 would not operate so efficiently atits upper cut-off or filter TBFa at its lower cut-ofi'. Therefore, to reserve'l i the eflicient operation of filters T F1' and,
  • TBF3 a simulating network may be substituted for filter TBFQ. It would be'nfecessary, of course, thatthis network simulate approximately the impedance of filter TBF2. A similar procedure could be followed if it were desired to eliminate either filter TBF1 or filter TBFf, or both of them.
  • the invention has been described mainly in connection with its application to the operation of band pass filters because the use of such filters involves a transmission improvement in two regions,.o11e just above the lower cut-offend the other ]ust below the upper cut-off.
  • the invention is equally applicable to the operatlon of low and high pass filters in parallel or in series. .In the case'of filters of this type the im'- provement in the transmission range of the filters would be just, below the lower .cut-off and just abovethe upper cut-off frequencies.
  • Another example of the use of filter.l impedance simulating networks is in the operation of directional or grouping filters at repeater stations and at the terminal stations of carrier current si aling systems. Here low.
  • a selective system comprising a common circuit, a plurality of filters with'respective mutually exclusive transmission ranges, said filters including terminal sec.
  • VA selective circuit comprising a plurality of filters with respective mutually exclusive transmission ranges, and corrective means to reduce the transmission loss 'of the filters transmitting the lowest and highest bands of frequencies in the neighM borhood of their respective lower and upper -Y ing their terminals connected to each other and corrective means comprising reactive elements connected across said filter terminals to reduce the transmission loss in the neighborhood of the lower cut-off of the filter transmitting the lowest band of frequencies and in the neighborhood of ⁇ the up'- per cut-offof the filter transmitting* the highestband of frequencies.
  • a selective circuit comprising a transmission line, a plurality of filters with respectivey mutually exclusive transmission ranges connectedto said line, and impedance corrective networks connected to said line to reduce the transmission loss inthe neighborhood of the lower cut-off of the filter transmitting the lowest band of frequencies and in the neighborhoodof the upper cutoff of the filter transmitting the highest band of frequencies.
  • a selectivey circuit comprising a transi mission line, a plurality of lters -each adapted to transmit a bandof frequencies,
  • any given filter acts as an -impedance corrective network for the adjacent filter in the neighborhood of the cut-0E frequency nearest the transmission band of the given filter
  • a selective circuit comprising .a trans- V,mission lline, aplurality of l band filters joined at one end to ysaid line so that certain frequencies may be diverted into. one filter and other frequencies into ,another filter,
  • a selective circuit comprising a transmission line, a plurality vof band filters joined at one end to said line so that certain frequencies may be diverted into one filter and otherl frequenciesjinto another filter, and a-pair of impedance networks connected to said line, one of""said networks simulating the impedance of a fictitious filter adjacent t'he'lowest filter in the lfrequency scale at the lower cut-off thereof, and the other of said networks simulating the impedance of a fictitious filter adjacent the highest filter in the scale at the upper cut-olf thereof.
  • a selective circuit comprising a transmission line, a plurality of filters with re-i spective mutually exclusive transmission ranges connected in parallel tosa'id line,y
  • a selective circuit comprising a trans-- mission line, a plurality of band filters conthe highest band of frenected in parallel to said line so that certain frequencies may be diverted into one filter and other frequenciesinto another filter, and a pair of impedance networks connected in parallel to said line, onek of said networks simulating the impedance of a ctitiousfilter adjacent thelowest filter in, the frequency scale, and the otheriof s aid networks simulating the. impedance 'of a fictitious filter adjacent thehighest filter in 4the/frequency Scale.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Filters And Equalizers (AREA)
US740528A 1924-09-29 1924-09-29 Selective signaling circuits Expired - Lifetime US1616193A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US740528A US1616193A (en) 1924-09-29 1924-09-29 Selective signaling circuits
FR593368D FR593368A (fr) 1924-09-29 1925-02-05 Circuits de signalisations sélectives

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE977521C (de) * 1951-10-13 1966-11-03 Siemens Ag Schaltungsanordnung zur Verminderung einer gegenseitigen Beeinflussung von eingangs- oder ausgangsseitig zusammen-geschalteten Filtern
US3771064A (en) * 1972-07-03 1973-11-06 Electronic Labor Inc Bidirectional signal processing means

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20020049714A1 (en) 2000-05-11 2002-04-25 Shunpei Yamazaki Communication system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE977521C (de) * 1951-10-13 1966-11-03 Siemens Ag Schaltungsanordnung zur Verminderung einer gegenseitigen Beeinflussung von eingangs- oder ausgangsseitig zusammen-geschalteten Filtern
US3771064A (en) * 1972-07-03 1973-11-06 Electronic Labor Inc Bidirectional signal processing means

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Publication number Publication date
FR593368A (fr) 1925-08-21

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