US1518495A - Selective circuits - Google Patents

Description

Dec. 9, 1 24. 1,518,495

' L. ESPENSCHIED SELECTIVE CI'RCUTTS Filed Sept. 26, 1919 3 Sheets-Sheet -1 g 2 l 2; 25 F E'fik;

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L. ESPENSCHIED SELECTIVE CIRCUITS Filed Sept. 26, 1919 3 Sheets-Sheet 2 INVEN TQR. L. E8 4 emschbed A FAI 3 Sheets-Sheet 5 INVENTQR. L.ES ensc/ued AT 0 EY L. ESPENSCHIED SELECTIVE CIRGUTTS.

Filed Sept. 26, 1919' Dec. 9, 1924- Patented Dec. 9, 1924,

UNITED STATES PATENTOFFICE.

LLOYD ESPENSCHIED, or nonLIs, NEW YORK, ASSIGITOR T AMERICAN 'rnnnrnonn [AND rnnrzemn coMrANY, A CORPORATION or new roan.

SELECTIVE CIRCUITS.

Application filed September 26, 1919. Serial NO. 326,521.

To all whom it may concern: Be it known that I, LL YD residing at Hollis, in the county of Queens and State of New 'York,have invented certain Im rovements in SelectiveCircuits, of which t e following is"a'spec'fication.

This invention relates to multiplex transmiss'ioncircuits and more particularly to arrangements whereby a plurality of Channels may be associated w'th acommon transmission circuit without interference between the channels. s v

One of the features of the invention resides in the provision of novel selective devices to prevent interference between the channels.

Another feature of the invention relates to a form of coupling device for coupling tuned selective circuits in such a manner as to obtain sharp selectivity and efficient transmission.

Another feature of the invention relates V to. the provision of means whereby a plural- -ity of channels may be serially related to a common transmission circuit in such a manner that the two sides of the transmission circuit will be balanced.

Other and further features of the inventiori will be clear from the following description when read in connection with the accompanying drawing, Figures 1 to 4 of which illustrate a plurality of embodiments of the invention.

'Referring to Figure 1, ML designates a transmission line over: which a plurality of transm'ssions may take place simultaneously. A common transmitting circuit TL v and a common receiving circuit RL are .as-

sociated with the line ML through a balanced transformer arrangement 10 and the line ML is balanced by an artifical line or network vMN, in" order to render the circuits TL and BL. substantially conjugate. A plurality of transmitting channels T T etc. are bridged across the common transmit ting circu t TL, whereby a plurality of signals may be simultaneously impressed upon the line ML for transmission to a distant station. In a similar manner a plurality of receiving1 channels, R R etc. are brdgecl across t e common. receiving circuit RL, whereby a plurality of signals simultaneo1rs1y transmitted over the line ML from a Esrnnscmnn,

may assume a wide variety of forms and for purposes of illustration a different form of selective device is shown associated with each of the channels of Figure 1; For instance, the selective device asso'ciated with the channel It, may comprise a pair of resonant circuits F, and F loosely coupled through a transformer comprising w'ndmgs 11 and 12. The windings Hand 12 also serve as inductances which, in conjunction with capacities 13 and 14, serve to tune the resonant circuits to a desired frequency.

Instead of us'ng the mutual inductances of the two windings of the transformer for coupling the two resonant circuits, an autotransformer arrangement may be used, as shown in connection with the resonant circuits F and F of the channel B In this case the circuits are tuned by means of condensers 15 and 16 and inductances 17 and 18, while a small coupling inductance 19 is shunted across the resonant circuits-F and F at the junction points. The self-induc- 'prsing the windings 11 and 12 of the channel R The arrangement associated with the channel It, is similar to that associated with 3,, except that the tunin inductances and ca acities are interchange thus the tuning in uctance 21 of the resonant circuit F is in shunt relation with respect to the channel, instead of in series, as in the case of inductance 18 of channel B So also the capacity 23 is in series instead of in shunt, with respect to the channel R The coupling inductance 24 is in all respects simiiar to the inductance 19.

Instead of an inductive coupling, 'a ca pacity coupling may be utilized, as illustrated in connection with the channel 8,. In this'case the resonant circuits F, and F, are meat means of inductances 25 and 26 and capacit'es 27 and 28, these capacities being shunted acrossthe channel and being relatively large in value. For

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coupling purposes capacities 29 may be serially included in the channel between the resonant circu'ts and for loose coupling these capacities should be relatively small in value.

If desired, a series-shunt coupling may be employed, as illustrated in connection with the channel B In this case the resonant circuits F and F are tuned by means of capacities and 31 and inductances 32 and 33,, while the two circuits are coupled by means of series capacit es 34 of relatively small value and shunt inductances 35 and 36 which are also of relatively small value.

Instead of shunt inductances of relatively small value, large shunt capacities may be substituted, asindicated in connection w'th the channel R in which the resonant cir- V cuits F and F are tuned by means of capacities 37 and 38 and inductances 39 and 40. The coupling in the case is obtained by means of small series capacities 41 and .ar e shunt capacities 42 and 43.

nstead of a shunt inductive coupling havingself-inductance fortuning the circuits and mutual inductance for coupling the circuits as shown in connection with channel R a capacity arrangement having mutual capacity for coupling the circuits and individual capacity for tuning the circuits, may be substituted as illustratedin connection with the transmittin channel T In this case the resonant circuits F. and F 5 comprise tuning lnductances 44 and 45, while tuning capacity is obtained from a condenser arrangement 46. This condenser arrangement comprises a plurality r the shunt inductive coupling associated with of plates, certain of which are individual I to the resonant circuits F and F and other plates which are common to both circuits. the capacity of the latter plates serving as a'mutual coupling capacity.

i A shunt capacity coupling equivalent to the channel R is illustrated in connection and inductances 54 and 55. these elements I being interchanged with respect to the corresponding elements shown in connection with the channel T The large shunt capacity 56 serves as a coupling element.

Instead of a series capacitative' coupling such as is illustrated in connection with the channel R a series inductive coupling may be used, as shown in connection with the transmitting channel T In this instance the resonant circuits F, and F. are tuned by means of inductances 57 and 58 and shunt capacities 59 and 60. Relatively large inductance elements 61 serially included in the sides of the channel between the resonant circuits F and .Frl, serve as coupling'elements. I i

In a similar manner the series capacities 34-and 41 of the coublina Elements of the receiving channels R and H may be replaced by large series inductances 66 and 73, as illustrated in connection with the transmitting channels T and T The small shunt inductances 67 and "68 of the channel T correspond to the similar inductances 35 and 36 of the channel R while the large shunt capacities 74 and 75 of the coupling element associated with the transmitting'channel '1 correspond to the similar capacities 42 and 43 of the receiving channel R 7 The several types of coupling elements illustrated in connection with the transmitting channels have a slight advantage over their prototypes illustrated inconnection with the receiving channels. in that they tend to reduce harmonics: for instance, the large shunt capacity of the condensers 46, 51 and 56 associated with the channels T T5 and T provide a shunt path for harmonies, of low impedance. So also the large series inductancesfil, 66 and 73 of the channels T T and T oiferrelatively large impedance to harmonics. thereby preventing the transmission of such harmonics from one tunedcircuit to the. other.

In the arrangement shownin Figure 1, the channels R R etc: T T etc. are all in bridged relation with respect to the comnon transmission circuits-BL and TL. F igure 2 illustrates a modified arrangement in which the channels are associated mutually in series with respect to the common transmission circuits RL and TL. Thus the channel R is associated with the circuit RL by including the shunt tuning capacity'l3 of the resonant circuit F serially in the transmission circuit R.. In a similar manner the receiving channel R is serially connected to the circuit BL by arranging the shunt tuning capacity 15 of the resonant circuit Ii in series with the transmission circuit RL. In

comprise capacity elements 30 and 31, said and need not be described.

In some instances the series arrangement shown in Figure 2 may be undesirable by reason of unbalances to ground and the partial short-circuiting of the terminal cir-i cuits. For instance, in the case of the channels T, and T',, if a vacuum tube is included in the channels, as illustrated in connection with the channel T then, with the filaments of the tubes grounded, as indicated in connection -with the channel T the terminal condenser 52 will be partially short-circuited over a path extending from the lower terminal of 52 over the lower side of tuuing in ductances 54 and 55 to the ground of the filaments and back" through the lower side of circuits F and F to the upper terminal of the condenser 52. Furthermore, the arrangement shown in Figure 2 is non-symmetrical with regard to the two sides of'the transmission circuits RL and TL, since the series connection of the channels are included in one side only of the common circuits, thereby tending to unbalance the two sides of the circuits. These objections may be overcome by means of the arrangement illustrated in Figure 3, in

which the channels are inductively associated with the common circuits RL and TL. The inductive connection permits of serially relating the channels to the common circuit and at the same time prevents shortcircuiting of the terminal circuit in the manner above described. By arranging the inductive connections so that half of the inductance thereof is inclined ineach side of the common transmission circuits RL and TL, unbalancing of said circuits will be prevented.

For example, the channel B, may terminate in a transformer 76, comprising three windings, one of which is serially included in the channel R the other windings being serially included, onein each side of the circuit FL. The channelR, may be coupled in a similar manner'bymeans of a transformer 77. In the case of the channel R since the resonant circuit F,v of Figure 2 terminates in a: shunt inductance 20, the corresponding channel R of Figure 3 may be associated with the circuit RL through a three-winding transformer 78, which not only serves as a means for assoresonant circuit F The same considerations apply to the transformer 79, which may be used for coupling the channel R, with the circuit BL. In the case of'channels R and R since the resonant circuits F5 and F terminate in shunt condensers,

the channels must be terminated in transformers 80 and 81, for the purpose of asso- T are associated with the common circuit TL. through' special transformers '84, 86 and 87. i

A similar arrangement is illustrated in Figure 4, in which, instead of employing tuned circuits for frequency separation, broad band filters are used. These filters are preferably of the type illustrated in the United States patents to George A. Campbell, Nos: 1,227,113 and 1,227,114, dated May 22, 1917, and are designed to transmit bands of frequencies of suificient width to allow for the transmission of signaling frequencies which extend over a considerable range, as is the case in the transmission of telephone currents. t

In Figure 4 transmitting channels T to T, inclusive, include broad band'filters BF BF,, BF and BF respectively, while the I corresponding receiving channels R, to R, inclusive, include broad band filters B,F,, B,F,, B,F and B F respectively. The channels T, to T inclusive, are associated with the common transmitting circuit TL through transformerslOl, 102, 103 and 104, each of which is balanced by means of windings included in each side of the circuit TL. In a similar manner the receiving channels R, to R, inclusive, are associated with the common receiving circuit RL through balanced transformers 111, 112, 113 and 114, of similar construction. By means of this arrangement the, channels are mutually arranged in series with respect to the common transmission circuit, while maintaining'the two sides of the common circuit balanced.

It will be obvious that the general principles herein disclosed may be embodied ferent from those illustrated," without (19- parting from the spirit of the invention as defined in the following claims.

What is claimed is: '1. A selective device comprising a pair of selective circuits, each circuit including inductance and capacity whereby the circuits may be tuned to the same desired frequency,

and means for loosely coupling the tuned circuits, comprising series and shunt impedance elements, one of which is inductive and the other of which is capacitative, and said'impedance elements being so proportioned and related with respect to each other and with respect to said tuned circuits as to roduce a greater discrimination against requencies onone side of the frequency to which the selective circuits are tuned than that due to the selectivity of the tuned circuits themselves.

2. A selective device comprising a pair of selective circuits, each circuit including inductance andcapacitywhereby the circuits ma be tuned to'the same desired frequency, meansfor loosely coupling the tuned circuits, comprising series and shunt impedance elements one of which is inductive, and said impedance elements being so proportioned and'related with respect to each;

other and with'respect to said tuned circuits as to produce a greater discrimination against frequencies on'one side' of the frequency to which the selective circuits are tuned than that due to the selectivity of the tuned circuits themselves.

3. A selective device comprising a pair of circuits, each including inductance and capacity whereby the circuits may be tuned to the same desired frequency, and means for loosely coupling the circuits, comprising impedance elements of two types, one type being indiyidualrto said circuits and the other type common to said circuits, one of said types of impedance elements being inductive and the other type being capacitative, and said impedance elements being so proportioned and related with respect to each other and with respect to said tuned circuits as to produce a greater. discrimination against frequencies on-one side of the frequency to which the selective circuits are tuned than that due to the selectivity of the tuned circuits themselves.

' 4. A selective device comprising a pair of tuned circuits, each'including inductance and capacity whereby the circuits may be tuned to the samedesired frequency, and means for looselycoupling the circuits, comprising impedance elements individual to said circuits and impedance elements common to said circuits one of said impedance elements being inductive, and said impedance elements being so proportionedand related with respect to each other and with respect to said tuned circuits as to produce a greater discrimination against frequencies on one side of the frequency to which the" selective circuits are tuned than that due to the selectivity of the tuned circuits themthe same desired frequency, and meansfor loosely coupllng saidcircuits, includin im- 1 pedance elements of two types, one 0 said types being shunted across said circuits and impedance elements of the other type serially connecting said circuits, one of said types of impedance elements being inductive and the other type being capacitative, andsaid impedance elements being so proportioned and related with respect to each other and with respect to said tuned circuits as to produce a greater discrimination against frequencies on one 1 side of the frequency'to which the selective circuits aretuned than that due to the selectivity of the'tuned cir-' cuits themselves.

6. A selective device comprising'apair of selective circuits, each including inductance and capacity whereby they may be tuned to the same desired frequency, and means for loosely coupling said circuits, including impedance elements shunted across said circuits and impedance elements serially connecting said circuits one of said impedance elements being inductive, and said and related with respect to each other and withrespect to said tunedcircuits as to produce a greater discrimination against frequencies on one side ofthe frequency to inductive reactance, and said. impedance elements being so proportioned and related with respect to each other and with respect to said tunedcircuits as to produce a greater discrimination against frequencies on one side of the frequency to which the selective circuits are tunedthamthat due to the selectivity of the tuned circuits themselves.

8. A selective device comprising a pair of selective circuits, each'including inductance and capacity whereby said circuits may be tuned to the samedesired frequency,

and means for loosely coupling said circuits, comprising an impedance in'shunt relation with respect to said circuit, and an impedance in series relation with respect to said circuit, one of said impedances having an inductive reactance, and said impedance elements being so proportioned and related with respect to each other and with respect to said tuned circuits as to produce a greater discrimination against freimpedance elements being so proportioned quencies on one side of the frequency to which the selective circuits are tuned than that due to the selectivity of the tuned circuits themselves.

9. In a multiplex transmission'system, a transmission circuit, a plurality of signaling channels associated with said circuit at one end thereof and adapted for transmission in the same direction, selective devices in each signaling channel and series conne tions between each channel and said transmission circuit, said series connections being balanced with respect to the two sides of the transmission circuit.

10. In a multiplex transmission system, a transmission circuit, a plurality of channels associated with said transmission circuit at one end thereof and adapted for transmission in the same direction, selective means in each channel and means in each channel for associating each channel with said transmission circuit, comprising a transformer having balanced windings in each side of the transmission circuit.

11. In a multiplex transmission system, a transmission circuit, a plurality of channels associated with said circuit one end thereof and adapted for transmis ion in the same direction, selective devices in each channel, and means for in efiect serially relating each channel to the transmission circuit, said means comprising transformers, each transformer having windings in each side of the transmission circuit and a winding in the corresponding channel.

In testimony whereof, I have signed my name to this specification this th day of September, 1919.

LLOYD ESPENjSCHIED.

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