US1502814A - High-erequency multiplex signaling system - Google Patents

Description

July 29 1924.

LM-EEH=EPJSCZFHEZD HIGH FREQUENCY MULTIPLEX SIGNALING SYSTEM Original Filed Sent. 30. 1919 I wi smto z llflf/velzsciad Patented July 29, 1924..

UNITED STATES PATENT OFFICE.

LLOYD ESPENSCHIED, 033 QUEENS, NEW YORK, ASSIGNOR T0 AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A. COREGRATION OF NEW YORK.

HIGH-FREQUENCY IMULTIPLEX SIGNALING SYSTEM.

Original application filed September 30, 1919, Serial No. 327,500. Divided and. this application filed April Te ((15 107mm it may concern:

Be it known that I, LLOYD ESPENSGHIED, residing at Queens, in the county of Queens and State of New York, have invented certain improvements in fliglrFrequency Multiplex Signaling Systems, of which the following is a specification.

T his invention. relates to high frequency multiplex signaling system and more particularly to a terminal circuit arrangement embodying the use of a common translating circuit adapted both to modulate the trans mitted current and to demodulate the high frequency received current.

This application is a division of my copending application Serial No. 327 500 filed September 30, 1919, entitled high frequency multiplex signaling systems.

In the multiplex signaling systems heretofore used which employ a plurality of carrier currents of various frequencies, it has been customary to insert in the transmittting and the receiving branches of the terminal circuit a translating device individual to each of said branches. It is the object of the present invention to adapt the'terminal circuit arrangement so that the processes of modulation, demodulation and amplification of the various currents in both the transmitting and receiving branches of the terminal circuit may be performed by a single translating device. Although the preferable form of translating device is a single thermionicvacuum tube or a plurality of such tubes in combination adapted to function as a single unit with respect to the two branches of the terminal circuit, yet any well known type of translating device such as the mechanical repeater may be used.

Another object of this invention is to provide a circuit arrangementof the general character described above in which the filters are inserted in the two-wire circuits, that is to say between the line circuits and the triple winding transformer which serves to connect the common translating circuit with the twowire vsignaling circuits.

Other and further objects of this invention will be apparent from'the following description when read in connection with the attached drawing of which Figure 1' shows an arrangement employing two triple winding transformers in which the third Serial No. 461,966.

winding of each transformer is connected in parallel with the output circuit of the translating circuit; and Figure 2 shows an arrangement in which a single triple winding transformer is used which is arranged for the transformation of both the high frequency and the low frequency currents.

Figure l v shows a variation of the type of circuit described in my copending application referred to hereinbefore, in which a single translating unit performs both functions of modulation and demodulation for the two sides of'the circuit, the variation consisting in the placing of the high frequenc} and the low frequency filters in the two-wire portions as distinguished from the four-wire portion ofthe circuit. The circuit arrangement shown in the upper part of this figure represents one of the terminal circuits for the reception or transmission of one of the bands of frequencies based upon a definite carrier frequency, which may be transmitted or received over the main transmission circuit ML. In the circuit arrangement L, represents a low frequency signaling circuit. which is connected with the windings of the triple winding transformer T and is balanced by the network N Interposed between the line L, and the said transformer, and the network and the said transformer. are low frequency band filters F and F The high frequency line L is connected with the windings of another triple winding transforn'ier T with which is connected a balancing network N adapted to balance the high frequency line. Interposed between the line and the said transformer, and'the network N, and the said transformer, are the high frequency band filters E, and, ll, respectively. The midpoints of two of the windings of each transformer, T and T connected with linesL and L are connected in parallel, the, said connection embracing one of the windings of the transformer T The third windings of the transformers T and T are connected in parallel, the said connection embracing one of the windings of the output transformer T of the translating circuit. Inductances C and C are inserted in the conductors connecting the said third windings of transformers T and T with the output transformer T, in order to prevent the passage of high frequency oscillations between the transformer T and T In the operation of this circuit low fre quency voice currents from line L will pass through the low frequency band filter F and will be impressed across the midpoints of the windings of the coil T with which the line L is connected. These signaling currents will in. turn be impressed by the coil 1 of the input transformer T upon the coil 2 of the said transformer, and will acordingly modulate the high frequency oscillations which are impressed upon the translating circuit by the source 3. The modulated high frequency oscillations will pass through the output transformer T and will be 1mpressed by the windingl of the transformer T upon the high frequency circuit L The high frequency currents are excluded from the low frequency circuit by inductances C and-C and filters F F The high frequency modulated waves will pass through the high frequency band filter F to the main transmission line ML, and thence to the terminal circuit at the opposite end of the said line. The modulated high frequency oscillations received over the transmission line ML will be conducted by the circuit L through band filter F to the midpoint of the windings of transformer T These oscillations will be impressed across winding 1 of transformer T and will pass through the translating device and be demodulated thereby. The low frequency demodulated current will pass through inductances C and G which offer substantially no impedance to low frequencies, to the winding 6 of transformer T and will impressed upon the low frequency line L passing through the band filter F The low fre quency currents are excluded from the high frequency circuit by condenser 5 and the high pass filters F F This circuit arrangement illustrates a method by which the high frequency and the low frequency currents may be impressed upon a common translating device by means of balancing coils which are connected effectively in parallel. It. should be understood that any number of terminal circuits similar to the one described may be connected with the main transmission line, the terminal circuits being made selective by the inscrtion in each branch high frequency circuit of a band lilter similar to F but adapted to transmit any desired band of frequencies for the specific terminal circuit. Further more, a low frequency signaling circuit L might be connected with the transmission line through a suitable low frequency filter F for the transmission of low frequency signaling current over the transmission line simultaneous with the transmission of the various bands of high frequency oscillations.

.FigureQ shows another variation of the general type of circuit which differs from the circuit arrangement shown in Figure 1, in. that the low frequency and the high frequency transformers are connectet mutually in series instead of in parallel as shown in Figure 1. These two transformers may be replaced by one transformer suitably designed to efficiently transmit both high and low frequencies. The coils designated and (4 represent the low frequency transformer and. the coils designated 7) and 6 represent the high. frequency transformer. i'irnother distinguishing characteristic consists in the use of a single balancing network N adapted to balance the high frequency line which may be connected with a phtuality of terminal circuits.

in the figure, L represents a low fre quency line, having inserted therein a low frequency band filter F and connected 'with two of the windings of the triple winding transformer T L represents a high frequency branch circuit having inserted therein a high frequency band filter F and connected with the opposite ends of the same two windings of the transformer T with which the line L is also connected. The midpoints of the said two windings of transformer T are connected with the coil l of tar input transformer T the other coil of which is connected across the input side of the duplex. translating circuit. The output side of the said circuit is connected by nicai'is' of the transformer T with the third winding of the said transformer T Bridged across the circuit L between the tiller F and the point of connection of the said circuit with the transformer T is a balancing circuit containing low freque11cy fil.- tcr F and network N which is adapted to balance the low frequency line L Bridged across the circuit L, between the filter F and the point of connection with the wind ings of the transformer T is a balancing circuit containing high frequency filter E and the network N, which is adapted to balance the main transmission line h'lL with respect to a plurality of terminal networks.

In the operation ofthis circuit low fre quency currents are received over the line L, and will. pass through the filter F and be impressed upon the coil 1 of transformer T The high frequency oscillations from the source 3 will be modulated in accordance with the low frequency signaling currents by the duplex translating circuit. The

modulated high frequency oscillations will be impressed by means of transformer T upon the third winding of the transformer T and will set up similar oscillations in the circuit containing the other two windings, which will pass tl'irough the high frequency filter F over the high frequency circuit L to the main transmission line ML. These high frequency oscillations cantranslating circuit,

not pass into the low frequency line L since the filter F, is adapted to transmit only low frequency currents. in a similar manner the received high frequency oscillations arriving over the line L, will pass through the higl'i frequency band filter ll, (assining that they are within that hand of ireniencies which this filter is adapted to pass) and will be impressed across the coil 2 of transformer T These high frequency oscillations will combine with the unmodulated carrier oscillations from the source and will be demodulated in the The low frequency currents derived thereby will be transmitted by the transformer T to the third winding of the transformer T and will be impressed upon the receiving circuit connected with the other two windings'of the transformer. These low frequency currents will pass through the filter F, into the low frequency line L, and actuate the low frequency naling apparatus associated therewith. "llhese low frequency oscillations will not pass back into the high freqiileucy circuit L since the filter F which is interposed between the two circuits, is not adapted to pass low frequency currents. It will be seen therefore that this circuit arrangement provides means whereby the modulation of the transmitted waves and the demodiiilation of the received waves may be performed by a single translating circuit, which is connected with a single two-wire circuit by means of a single triple winding transformer. Furthermore, this circuit arrangement shows a method whereby a single net work may be utilized with a plurality of terminal circuits to balance the main trans mission line with which the plurality of terminal circuits may be connected.

Since the circuit is balanced with respect to the conjugate transformer by means of the networks which are designed to approximate electrically the line circuits connected with the end of the transformer opposite that to which the network is connected, the translating circuit may be operated so as to give greater amplification than the loss within the circuit itself without producing singing around the circuit.

Although this invention has been disclosed as being embodied in a particular form and arrangements of parts it is to he understood that it is capable of embodiment in other and different forms without departing from the spirit and scope of the appended claims,

l Vhat is claimed is:

l. in a signaling system, the combination with a high frequency transmission circuit, of a low frequency signaling circuit, and a translating circuit" interlinking said transmission and said signaling circuits and having means common to the transmitting and receiving paths of the oppositely traveling currents from said transmission circuit and said signaling circuit to modulate the curren from the said. signaling circuit and to demodulate the currents from the said transmission circuit and means to impress the modulated and demodulated currents upon the transmission and the signaling circuits respectively.

2. In a signaling system, the combination with a high frequency transmission line having a high frequency band filter and a balancing network connected therewith, of a low frequency circuit having a low pass filter and a balancing network, a translating circuit common to the said high frequcl'icy line and low frequency circuit, and means to impress currents from the said high fre quency line and the said low frequency circuit upon the said translating circuit, the said translating circuit having means to modulate and demodulate the impressed min-rents 3. In a signaling system, the combination with a high frequency circuit having high frequency band filters and a balancing net work associated therewith, of a low frequency circuit having low pass filters and a balancing network associated therewith, a translating circuit common to both. the high frequency and the low frequency circuit, a transformer coni'iecting the said high frequincy and the low frequency circuit with the input and the output sides of the said translating circuit, the said translating circuit having means to modulate and de modulate themurrents from the said low frequency and the said high frequency circuits respectively.

in a signaling system, the combination with a h gh frequency circuit of a low frequency circuit, a translating circuit having a frequency changing device connected therewith, a conjugate transformer coupling the said high frequency and the said low frequency circuits to the said translating circuit, and a high frequenc band filter and a low pass filter insertedin the said high frequen j and the said low frequency circuits respectively between the said circuits and the said transformer.

5. In. a signaling system, the combination with a high frequency circuit of a low frequency circuit, a translating circuit, a conjugate transformer connecting the said high frequency and the said low frequency circuits to the said translating circuit, the said transformer having a plurality of windings each containing a high frequency and a low frequency coil in series for the transformation of high frequency and low frequency currents,

6. in a high frequency signaling system, the combination of a source of low frequency signaling current, a source of high &

frequency current, translating circuit having means common to the transmitting and receiving paths of the oppositely traveling currents from the said sources to modify both the transmitted and received currents, means for impressing the said currents upon the said translating rircuit and frequency selecting means associated with the said source of signaling current and the said source of high frequency current whereby interference between the respective sources is prevented.

7. In a high frequency signaling system, the combination of a low frequency signaling circuit, a high frequency transmission circuit, a translating circuit having common means to modulate and demodulate the transmitted 'and received currents respectively, high frequency and low frequency transforming means connected mutually in series for impressing said currents upon said translating circuit, and frequency selecting means associated with the said signaling circuit and said high frequency circuit whereby interference. between the respective circuits is prevented.

8. A duplex system comprising a low frequency line, a high frequency circuit, a modulator-detector circuit adapted to modulate currents passing in one direction between said lineand said circuit and to detect currents passing in the other direction there between, a transformer coupling the said low frequency line and the said high fie quency circuit to the said modulator-detector circuit, a network for balancing the low frequency line and a filter for reducing the passage of high frequency currents to the said network.

9. A duplex system comprising a low frequency line, a high frequency circuit, a modulator-detector circuit adapted to modulate currents passing in one direction between said line and said circuit and to detect currents passing in the other direction there between, a transformer coupling the said low frequency line and the said high frequency circuit to the said modulator-detector circuit, a network for balancing the high frequency line and a filter for reducing the passage of low frequency currents to the said network.

10. In a carrier current system, a hybrid the said line, a hybrid coil and a second high pass filter.

13. In a carrier current system, a high frequency line, a low frequency line, means connecting said lines comprising a low pass filter adjacent said low frequency line, a high pass filter adjacent said high frequency line, a hybrid coil between said filters, a

branch circuit containing a high pass filter and a balancing network for said high frequency line connected between said low pass filter and said hybrid coil, a second branch circuit containing a low pass filter and a low frequency balancing network connected between said first mentioned high pass filter and said hybrid coil and a detector having its input circuit coupled to said hybrid coil and its output circuit coupled thereto in conjugate relation with respect to the said first coupling.

14. In a carrier current system, a high frequency circuit, a low frequency circuit, a single repeating device connected to said circuits to repeat low frequency currents from said low frequency circuit as high frequency currents to said high frequency .circuit and to repeat high frequency currents from said high frequency circuit as low frequency currents to said low frequency circuit and individual balancing means connected with the said high frequency and the said low frequency circuits at the points of connection of said circuits with the said repeater for simulating the impedances of both the said circuits.

In testimony whereof, I have signed my name to this specification this 15th day of April 1921. r

LLOYD ESPENSGHIED.

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