US1577778A - Carrier-signaling system - Google Patents

Description

March 23 1926.

'3. WHITE CARRIER SIGNALING SYSTEM Filed Sepic 5, 1925 UNITED STATES PATENT OFFICE.

CHARLES WHITE, OF VEST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIO COMPANY, INCORPORATED, 01 NEW YORK, N. Y., A CORPORATION OF NEW YORK.

,CARBI ER-SIGNALING SYSTEM.

Application'filed September 5, 1923. Serial No. 661,008.

To all whom it may concern:

Be it known that 1, CHARLES \Vnrrn, a citizen of the United States of America, residing at West Orange, in the county of I? and State of New Jersey, have invented certain new and useful Improvements in Carrier-Signaling Systems, of

' which the following is a full, clear, concise,

and exact description.

This invention relates to a carrier signaling system.

According to the ordinary practice in multiplex carrier wave telephone systems the transmission and receiving branches at each end of each high frequency channel of the system are coupled to low frequency circuits or lines terminating locally or extending to distant stations.

The low frequency circuits or lines may be two-way circuits wherein signals are transmitted in opposite directions over the same circuits or two one-way circuits in which the signals are transmitted in one direction over one circuit and in the opposite direction over the other circuit.

A two-way low frequency circuit, ordinarily known as a two-way circuit is coupled to a transmitting branch and associated receiving branch of a high frequency channel by means of a hybrid coil and associated low frequency line balancing network.

The two one-way low frequency circuits, commonly known as a four-wire circuit, are ordinarily connected one to a transmitting branch and the other to the associated receiving branch of the high frequency receiving channel.

Some of the channels of the multiplex carrier telephone system may be terminated in two-wire low frequency circuits and others in four-wire circuits. Furthermore, one end of a high frequency channel may be terininated in a two-wire circuit and the other end in a four-wire circuit.

Depending upon service conditions, a'high frequency channel of such a multiplex carrier telephone system may for a period of time be coupled to a two-wire circuit and for another period to a four-wire circuit. Furthermore, it is frequently desirable to quickly effect a change in the character of t e minat n f 09s 9 2? 9? th hi h frequency channels of a multiplex carrier telephone system.

This invention contemplates switching arrangements by which such a change in carrier channel termination may be quickly effected. l

Another feature of the invention relates to the provision of signal receiving apparatus which may be associated with either a two-wire or a four-wire circuit and the high frequency channel with which the appropriate low frequency circuit is coupled;

The apparatus and circuits illustrated in the drawing represent that required at a terminal station of a multiplex carrier telephone system.

As is well known, a multiplex carrier telephone system comprises a high frequency main line terminating at each end in a plurality of transmitting and receiying branches. The transmitting and receiving branches are associated in pairs and coupled to terminating low frequency circuits or lines. Carrier currents of different frequencies are employed for the different channels of the system. In the particular system illustrated, the carrier frequencies for transmission in one direction are comprised within a frequency range entirely different from that of the frequencies employed for transmission in the opposite direction.

For. the purpose of the present invention, it is not necessary to disclose an entire multiplex carrier telephone system but only the apparatus required at one of the terminal stations thereof.

lhe portion of the system illustrated in the drawing comprises a high frequency main line ML coupled by means of transformers TT and RT to the transmitting and receiving branches of the various chan nels of the system.

A single high frequency transmitting branch TU is shown in detail while three others, T6 TC 'and TC are indicated."

likewise, one receiving branch RG is shown in detail while three others, RC RC, and, RC, are indicated. i

The various transmitting branches are similar except as to the difference in the constants required due to the different freqieaer te ier c rren t.)

channels, so that a description of one transmitting branch will sufiic.

The transmittingbranch includes a niodulator hi to which carrier current of the frequency assigned to the channel is supplied from an oscillator C and a transmitting iand filter TBF, v

The modulator M, may be of any well known type, such, for example, as an electronic valve of the type disclosed in Fig. 42 of the article entitled Carrier current telephony and telegraphy by Colpitts and Blackwell, published in the Transactions of the American institute of Electrical Engr neers, Vol. 4.0, 1921.

The transmitting band filter TEE, which may be of the type disclosed in U. S. patent to Campbell, No. 1,227,113, May 22, 1917, is designed to pass currents of the carrier frequency assigned to the channel and of the frequencies within the upper or lower side band thereof and to suppress currents of all ther frequencies.

The receiving branches are alike except as to the constants of some of the apparatus thereof due to he different carrier frequen cies employed in the different channels. Consequently, a description of one such branch will suffice.

The receiving branch RC, includes a receiving band filter RBF,. a demodulator DM an amplifier A a low pass filter LPF,, a high pass filter HPF, and a rectifier R The receiving band filter RBF,, of the type disclosed in the Campbell patent supra, is designed to pass currents of the carrier frequency assigned to the channel and of the frequencies within the upper or lower side band thereof and to suppress currents of all other frequencies.

The demodulator, amplifier and rectifier may be of any well known type, such as the electronic valve type disclosed in Fig. 42 of the Colpitts and Blackwell article supra.

The low pass filter LPF of the type 'dis closed in id Campbell patent, is designed to pass currents of frequencies below tlu upper limit of the voice range and suppress currents of higher frequencies. The high pass filter, also of the type disclosed in the Campbell patent, is designed to pass currents above the upper limit of the voice range and to suppress currents of lower frequencies; I

The input of the transmitting branch TC, and the output of the receiving branch RC may be terminated in a two-wire low frequency circuit or a four-wire low frequency circuit.

In order that the termination of the transmitting and receiving branches of a high frequency channel may be readily and quickly changed, switching apparatus for this purpose is provided.

This switching apparatus comprises eavers switches H5 HS HS, and HS When these switches are in the position shown in full lines, the transmitting branch TC is connected to one of the one-way circuits C and the receiving branch RC is connected to the one way circuit C These two one way circuits together form a four-wire low frequency terminating circuit.

When the switches are in their dotted line positions, the transmitting branch TC, and receiving branch RC, are coupled to a two-wire low frequency terminating circuit C, by means of hybrid coil 1 and its associated low frequency balancing network if. The hybrid coil and its associated balancing network serve to conjugately relate the trans mitting and receiving branches with respect to the connected two-wire low frequency terminating circuit.

Some two-wire low frequency terminating circuits extend to stations equipped for transmitting thereover 16 cycle signaling current, while others extend to stations equipped for transmitting thereover 135 cycle signaling current. Usually, the stations in which the distant end of the fourwire low frequency circuits terminate are equipped to transmit thereover 135 cycle signaling current.

It is, therefore, necessary that the signal receiving and transmitting apparatus atthe carrier terminal station connected to the system be of a type suitable to receive and transmit signaling current of the proper frequency.

Therefore, at the terminal station there is provided a source 2 of 16 cycle signaling current and a source 3 of 135 cycle signaling current. There is also provided a receiving relay 4 responsive to the 16 cycle ringing current and a signal receiving relay 5 re sponsive to the 135 cycle signaling current transmitted from the respective distant stations over their connecting two-wire low frequency lines or circuits. Relay 5 is also responsive to 135 cycle signaling current transmitted over a at wire circuit from a dis tant station.

Switches VS, and HS control the connection of the proper receiving relay to the connected terminating circuit and switches VS, control the connection of the proper source of signaling current to the connected terminating circuit. The switches V8,, VS, and HS, are shown in their full line position connecting the proper receiving relay and source of signaling current to the four-wire terminating circuit.

The operation of the system as shown and as thus far described is as follows he 135 cycle signaling current incomi over the low frequency circuit C actuates relay 5 which opens its contact, releasing relay 6 The closure of the contact of relay- 6 short-circuits the frequency determining circuit of oscillator 0 so that the flow of carrier current over the main line from the terminal station is interrupted.

When a signal is incoming over the highfrequency main line ML as indicated by the cessation of flow of the carrier current, relay '4' in the output circuit of rectifier ll, releases, causing the lighting of a signal lamp 8 and the operation of relays 9 and 10. Relay 9 connects the source 3 of 135 cycle signaling current to the low frequency circuit C Relay 10 closes .its upper contact thereby short-circuiting a winding of the hybrid coil 1 and pr venting singing during the ringing operation.

When it is desired to terminate the transmitting and receiving branches TC, and EC, in a two-wire low frequency circuit equipped with transmitting and recelvmg signal apparatus of the 135 cycle type, the switches HS H8 H3 HS and H8 are moved to their dotted line positions and switches VS and VS are left in their full line position. The 135 cycle signaling current incoming over low frequency C11C111l7 C actuates receiving relay 5 as before, causing the release of relay 6 so that transmission of carrier current over the main line is interrupted. I

When a signal incoming over the high frequency line is indicated by the interruption of the flow of carrier current thereover, relay 7 releases as before, causing lamp 8 to light and relays 9 and 10 to operate. Relay 9 connects 135 cycle ringing current from source 3 to the low frequency circuit.

Relay 10 functions as before, shortcircuiting the winding of the hybrid (,Oll l. It also opens its lower contact thereby disconnecting relay 5 from the low frequency circuit during the ringing operation.

It is assumed that low frequency line C is equipped at its distant end Withapparatus for transmitting 16 cycle rmgmg current and with signal receiving apparatus responsive to 16 cycle ringing current transinitted from the carrier terminal station.

When the transmitting and receiving branches of the high frequency channel are to be terminated in the two-wire low frequency line or circuit C, switches H HS; and HS, remain in their dotted line positions, switches VS, and VS, are moved to their dotted line position and switch HS, is moved to connect to the terminals of the low frequency line O Switch HS may be in either of its positions.

The 16 cycle signaling current incoming to the carrier terminal station over low frequency circuit C, actuates relays: which releases relay 6 thereby interrupting the flow of carrier current over the main line.

Ringing signals incoming over the main line, as indicated by the absence of carrier current therefrom, release relay *3 wheresuch channel in either fouuwirc or a two wire low frequency line and for connecting the proper signaling apparatus to the connected terminating circuit, it is to be understood, of course, that hothends of ahigh frequency channel may be similarly equipped and both ends or one end only of all other channels may be similarly equipped.

The rectifier relays of the other receiving branches RC RC and RC, are indicated by relays 17, 27 and 37. Each of these relays controls a lamp similar to 8 and relays similar to 9 and 10 associated with their respective receiving branches. The operating circuit for relays 9, l0 and lamp 8 in- 1? cludes the normally open contact of relay 7 and the normally closed contact of one of the relays 17, 27 or 37." These normally closed contacts normally short-circuit resistance 38 and relay 39 so that so long as one of the relays 7, 17, 2'? and 37 is energized, relay 89 will not operate. However, when all of these relays 7, 17, 27 and 37 are re leased as would be the case upon a failure of the main line ML, relay 39 would then operate to close the circuit of an alarm signal 40. The combined resistance of relay 39 and resistance element 38 is so great, however, that when included in circuit with relays 9 and 10 of receiving branch RC, and the similar relays of the other receiving branches which are now all connected in parallel, the amount of current received by each of such parallel connected relays is insufficient to cause the operation thereof. Therefore, no signaling current is connected to any of the low frequency terminating cir' cuits when the high frequency line fails, but an alarm signal is given.

The circuit including relays 9, 10 and lamp 8 ray also include a switch 11 whereby this circuit may be opened should the oscillator at the distant terminal. supplying carrier current received by receiving branch RC fail for any reason. The other receiving branches may be similarly equipped.

The invention set forth herein is of course, susceptible of various other modifications and adaptations.

The invention claimed is:

1. In a signaling system, a carrier wave channel terminating .in a transmitting branch and a receiving branch, a two-Wire low frequency circuit, a four-wire low frequency circuit, two sources of low frequency Rel ay 7 Kill signaling current of respectively difierent character, two low frequency signal receiving branches and two-Way switches which, when in one position connect the two-Wire low frequency circuit to the transmitting and receiving branches and to one of said sources of low frequency signaling current and one low frequency signal receiving branch and, when in the other position, connect the four-Wire low frequency circuit to the transmitting and receiving branches and to one low frequency signal receiving branch.

2. In a signaling system, a carrier Wave channel terminating in a transmitting branch and a receiving branch, a two-Wire low frequency circuit, a tounwirc low frequency ci1cuit, sig11al receiving apparatus, and two-position switches which When in one position connect the two-Wire low fre quency circuit to the transmitting and receiving branchesancl the signal receiving apparatus to the connected low frequency circuit and when in the other position connect the founwire circuit to the transmitting and receiving branches and the signal receiving apparatus to the incoming leg of the four-Wire circuit.

In Witness whereof, I hereunto Subscribe ny name this 29th day of August A. 1)., 30

0 HA R LES XVI-UTE.

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