US1999346A - Two-way telephone system - Google Patents

Description

April 30, 1995. E. R. TAYLOR ET A1.

TWO-WAY TELEPHONE SYSTEM Filed June 16, 1931 v KMX wam h.

ATTORNEY UNETE STATES PATE 1,999,346 TWO -WAY TELEPHONE SYSTEM Edmund R. riaylor, New York, N. Y., and Doren Mitchell, Martinsville, N. J., assignors to American Telephone and Telegraph Company, a corporation oi" New York Application June 16, 1931, Serial No. 544,891 10 Claims. (Cl. 179-170) This invention relates to systems for the transnormally disabled channel at the receiving end mission of energy between distant stations for the of the system. production of some desired over-all effect. More The applicants transmission C0nt101 apparaparticularly, the invention relates to two-way teletus is preferably COllned t0 the terminal Sta- 5 phone systems having wave-responsive devices for tions, as distinguished from the intermediate Centrelling transmission, such as singing supradio stations, and is of such a nature that, should pressors and echo suppressors. c it be desirable to shift the operation of the system In a long telephone system it is often desirable, from the use of control currents to the control of in Order to prevent singing, to have one or both transmission by voice waves without special curio of the oneway paths normally disabled at one Tents, Only miner and readily made alteratiOnS or more points. It follows that means must be Would be required. provided whereby the voice waves will cause the These and other features and advantages of removal of any such disability normally foundon the aDDliCants methedsf and means fOr transthe path Other which thesewaves are to be transmission control will be understood when the foli; mitted. lowing detailed description of one desirable em- The system, however, may include what will be bodiment of the invention is read with reference hereinafter termed a mutable 1ink-that is, a. to the accompanying drawing, which shows dialink capable of or liable to change (from internal glamniateally, and in part schematically, the or external cause) which may give rise to interalJplieatiOn t0 a 1011s tWO-Way telephone system :o fering energy, or, more specifically, a link speincluding a radO linkoiauy subject to noise, fading (in the case of radio With reference t0 the details 0f the drawing, transmission) or change of impedance. In suon there is disclosed a two-Wav telephone system eX- a case, the wave-responsive devices on the receivtending frein Station W at the left t0 the distant ing side of the mutable link, when made suiii- Station E at the right- The system may be eX- ciently sensitive to operate on weak speech entended t0 the left from StatiOn W OVer the tWO- ergy, are liable to false operation by the interwire circuit L, which is connected through the fer-ing energy originating in the mutable link. usual hybrid COil and iS balanced by the llsllal This difliculty is removed if control currents are network. Likewise, the system may be eXtended employed and the wavcyesp0nsive devices cn the to the right from station E over the two-wire circuit L', which is connected through a hybrid coil spend exclusively to the frequencies of the control and balanced by a network. The system extendcurients. These control waves not only are easier ing betWeen StatiOIl W and StatiOIl E takes the to detect, in spite of interfering noise waves, than form of a four-wire circuit. The intermediate the Speech Waves7 being Conned to a, narrow frcportion of this four-wire circuit consists of a radio :1,3 quency band, but also have the advantage that link extending from station W at the left to statliey are applied suddenly with full amplitude, tion E at the right. It will be understood that producing a prompt and positive operation of the station W may be at a great distance from stae transmission controlling relays. tion W and that station E' and E may be sep- The applicants invention is particularly apalated by a great distance- 40 plicable to systems such as that suggested above. The Path adapted for transmission fmm left More particularly, it is applicable to the shortt0 Tight comprises the Oneway Wire Section LW wave radio-telephone systems used for transconnecting Stations W and W" the radio link be Oceanie Communication tween the transmitting antenna nt and -the ref: In general, the applicants apply the control ien/mg ajntenna.A2" and the-recenfmg WH? Sec" i cu1rents`preferably, two or more control curnon LW extending from station E to staimn E' ,L 1 The path adapted for transmission from right to lenYS of @mlent frequencles m each dlrectlonleft comprises the one-way wire section LE', the 12g itedpenods 1/Ihm n? V10 energy 1s bemg radio link between antennae A1' and A2, and the n m D e cause e comm lequency`or any receiving wire section LE. It will be noted that 50 one. of, a ,plurality of @Html frequencies-t0 the left to right channel is normally disabled at maintain disabled the recewing channel which is the pol-n1; 1, at Station W and at the point d at staadapted for transmission from the mutable link. tion E. Likewise, the channel for transmission and Cause the Voice Waves 011 the transmitting from right to left is noi-many disabled at the point side of the mutable link to disconnect the sourceb at station E and at the point d at station W.

'l` GFFICE or sources-of control current and thus clear the Associated with the wire section LW at stationquencies which are generated and applied to the path LW at station W. rlhe alternating-currents so generated and applied to the transmission paths are the control currents.

Consideration being given particularly to transmission from station W to station E, the frequencies f1 and f2 are normally sent over the path LWV to station W', are there applied to the radio transmitter and the transmitting antenna A1, are picked up at the distant station E in the antenna Az', are applied to the radio receiver and are then sent over the path LW to station E. There each control frequency passes through the appropriate filter and operates an amplifier-detector, fi operating Vamplifier-detector 3E' and f2 operating amplirier-detector 4B'. Relays 3| and di are connected in the output circuits of amplifier-detectors Sil' and All', respectively. 1t will be understood that as long as the control frequencies are transmitted these relays 3i and lli are maintained in operated condition and that the operation of either one of these relays serves to disable the path LW at points d. While it is not of the essence of the invention, it is advantageous to use two or more control currents of diirerent frequencies, which are usually outside the voice range. Thus if selective fading eliminates one of the control frequencies in the radio link, it is likely that the other-or one of the others, if more than two control frequencies are used-will be transmittedwith suincient strength to maintain one of the relays' operated to disable the transmission path at point'd. The generators of frequencies fi and f2 and the amplifier-detectors Bil and i are understood to represent any suitable number of generators and corresponding ampli-- fier-detectors.

In the system specifically disclosed the transmission of control currents from station E to station W is the same as the transmission in the opposite direction.

At station W the amplifier-detector iii, controlling certain relays to be discussed hereinbelow, is connected to the path LW atY point c and is responsive to the voice waves. At the distant station E the amplifier-detector 2t is connected to the path LW at point c and, like amplifier-detector iti, responds-to the voice waves. Likewise, amplifier-detectors Eil' at station E and 2E at station W respond to voice waves traveling from right to left.

If voice waves from circuit L enter the transmission path LW, they pass through a volume control device and a one-way amplifier to the point a at the input of a delay circuit. At this point a portion of the voice energy is diverted to operate amplifier-detector l. Relays il, i2 and i3 are operated by this amplifier-detector. Relay serves to remove the disability from the path LW at point b. The operation of relay i2 disables balanced coil BCi and prevents the further application of the control currents of frequencies f1 and f2. it should bev noted at this point that the filter in the output of the coil BCi is designedto prevent theapplication to the transmission path of transients in the voice range set up by the operation of the relay I2. The operation of relay I3 disables the balanced coil BCz in the opposite receiving path LE, thus preventing transmission over that path. It should be noted that if relay 2i has operated before the operation of amplifierdetector IEP, the relays i2 and i3 will not operate. This feature will be discussed hereinbelow.

The transmission of the voice waves beyond the point a in path LW is held up slightly in the delay circuit, time thus being given for the clearing of the channel at point b by relay and the removal of the control energy by the operation of relay i2.. The speech currents now divide in the hybrid coil, half of the energy being dissipated in the balancing network and the other half being transmitted on to the radio transmitter at station W'. At the distant end of the radio link the voice waves are picked up in the radio receiver at station E and are then sent on over path LW to station E. By the time the voice energy reaches station E the interruption of the control energy will have caused the release of relays 3 I and 4 I and accordingly the disability will have been removed from the path LW at the point d. Voice waves now pass through the balanced coil BCz to the point c. At this point the waves cause the operation of amplifier-detector 2li and relay 2|', unless relay i3' has operated, as will be discussed hereinbelow. the output circuit of amplifier-detector lil (associated with the opposite transmitting path LE) and the circuits of relays Il', I2 and I3. This operation secures control of the system at station E and prevents breaking in by the subscriber connected to circuit L. Furthermore, echoes of the voice waves traveling Yfrom left to right, which may enter the path-LE and operate the amplifierdetector Hi', are prevented from interfering with the transmission over the path LW and from causing false operation of the relays i i and l2. Beyond point c' the voice waves pass through the delay circuit, which has introduced the delay necessary for the operation ofrelay 2|', the volume control device and the one-way amplifier' to the circuit L'.

It should be noted in connection with transmission from station W to station E that during the transmission of the voice waves relay |3 is held operated. Accordingly, even if relays 3| and 4| should both release momentarily because of oontrol frequency fading in the radio link, the balanced coil BC2 is held disabled and voice waves in the path LE cannot reach the point c to operate amplifier-detector 2i) and relay 2|. in other words, if the voice waves in path LW reach the point ci in time to take control of the left end of the system at station W through the operation of relays Il and I3, later arriving energy in the opposite path LE cannot interrupt this control. If, however, the voice energy in path LE has reached point c without interruption, amplifierdetector 26 and relay 2| will operate, and the control of the system at station W is given to the subscriber connected to station E.

The operation of the system in connection with transmission from rightto left is, in the system specifically disclosed, in connection with transmission from left to right. Control frequencies fi and f2 are applied during the silent periods to the path LE', the filter atthe output ofthe coil BCi passing the control frequencies but excluding the transients in the voice range. These control frequencies reach the station W and hold relays 3| and 4| (or one The operation of relay 2| breaks the same as that described of them, at least) operated to disable the path LE at point d. When voice Waves travel over the circuit L and the path LE', amplifier-detector l e' is operated. Relay ll removes the transmission path disability at point 79'; relay l disables the coil B01 and thus prevents the further application ci the control frequencies; and relay i3 disables the opposite transmission path LW at the coil B02. When the voice Waves reach the station W, the path LE has been rendered operative by the release of relays 3l and di, and the voice waves travel on to the point c, unless relay i3 has operated in the meantime. As described above, the operation oi ainpliermdetector 2i) and relay 2i secures control by preventing interruption due o later arriving voice Waves in the opposite path LW. The voice Waves in path LE are novv free to pass on to the connected circuit L.

It remains to point out several advantages of the applicants arrangements for transmission control:

The receiving path at either of the stations W and E is normally held inoperative by the control currents; accordingly, noise energy coming from the radio link cannot pass over this receiving path to produce false operation of the transmission control device the voice responsive control devices be made very sensitive, so as to operate on the Wea-zest speech.. This sensitivity of the voice responsive apparatus connected to the receiving path serves to insure the prevention of false operation by echo currents returning over` the opposite transmitting path, as has been described above. Accordingly, the receiving volume is practically independent of noise originating in the mutable (radio) link.

It has been stated above that the control currents are usually of frequencies outside the voice range. Since these control currents are transmitted from the radio transmitters only when no speech is being transmitted, no additional load capacity is required in these transmitters. As has been indicated above, the filters in 'the inputs of ampiiiier-dctectors Sil, til and fifi pass only the control frequencies and thus prevent operation oi these ainplier-detectors by energy other than the control energy. it has been shown above that While a single control frequency may be employed in each direction oi transmission, it may be preferable to use tvfo or more control freduencies, in order to furnish some degree of insurance against damaging fading in the radio link and the resultant undesirable transmission or" radio noise.

While the invention has been disclosed specifically in one desirable embodiment, it is -to be understood that the applicants methods of and apparatus for transmission control may take other and widely different forms within the scope of the appended claims.

What is claimed is:

l. In a tivo-way systeni for the transmission of energy, two paths adapted for transmission in opposite directions, means near the transmitting terminal of one oi said paths for applying control energy to said path, means near the receiving terminal of said path responsive substantially only to said control energy for maintaining said path in disabied condition, means near the transmitting terminal of said path responsive to the energy transmitted thereover to produce the desired over-all effect for preventing the application thereto of said control energy, and means near the transmitting terminal of said path responsive to said energy transmitted to produce the desired overuall effect for controlling the transmission over both the transmission paths, near said terminal, said last-mentioned means being independent of the application to the system or the Withdrawal therefrom of control energy designed to pass over the receiving end oi the opposite path.

2. ln a tvvo-Way system for the transmission of energy, including a iii-st path adapted for transmission in one direction and a second path adapted for transmission in the opposite direction, the method of transmission control which consists in applying control energy to the rst path near the transmitting end thereof, causing said control energy to maintain the rst path in disabied condition near the receiving end thereof, causing the energy transmitted for the production of the desired over-ali eiiect, as it travels over the transmitting end ci the first path, to prevent the application of the control energy thereto, causing said energy transmitted for the production of the desired over-all effect, as it travels over said transmitting end, to control the transmission over said iirst and second paths at that end of the system, and preventing the interruption of the last-nientioned control by the application to the system or the Withdrawal therefrom of control energy designed to pass ovei said second path.

3. in a two-Way system for the transmission of energy, a iirst path adapted for transmission in one direction, a second path adapted for transmission in the opposite direction, means near the transmitting end of said first path for applying control energy thereto, means near the receiving of said rst path responsive substantially only to said control energy for maintaining said path in disabled condition, means near the transmitting end of said irst path responsive to the energy transmitted to produce the desired overall eiiect for preventing the application of said control energy, means similarly responsive near the transmitting end of said rst path for controlling the transmission over said path and the opposite sect-ion of said second path, and means near the receiving end of said second path and responsive to energy therein of earlier arrival than energy in the first path for rendering the paths exempt from control by energy in the iirst path, the control. ci the transmitting end of said Erst path being independent of the application to the system the withdrawal thereirorn of control energy designed to pass over said second path.

f-i. in a tivowv/ay signal transmission system, including two paths adapted for transmission in opposite directions, the method of transmission control which consists in applying control energy to each path when said path is not being used for signal transmission, causing the control energy applied to a path to disable said path, causing the signal energy applied to the transmitting end of apath to interrupt the application of the control energy thereto and to control the transmission over the transmitting end thereof, and rendering a path immune to prevention or interruption of the signal control thereover by the application to the system or the Withdrawal therefrom of control energy designed to pass Over the opposite path.

5. In a two-way transmission system, including two paths adapted for transmission in opposite directions, the method of transmission control which consists in applying control energy to each path when said path is not being used for signal transmission, causing the control energy applied to a path to disable said path near its receiving end, causing the signal energy applied to the transmitting end of a path to interrupt the application of the control energy thereto and to control the transmission over the transmitting end thereof and the receiving end of the opposite path, and rendering a path immune to prevention or interruption of the signal control over the transmitting end thereof by the application to the system or the withdrawal therefrom of control energy designed to pass over the opposite path.

5. ln a tivo-way system for the transmission of energy, including a iirst path adapted for transmission in one direction and a second path adapted for transmission in the opposite direction, the method of transmission control which consists in applying control energy to each path near the transmitting end thereof, causing said control energy to maintain the path to whifh it is applied in disabled condition near the receiving end thereof, causing the energy transmitted for the production of the desired over-all efrect, as it travels over the transmitting end of one of said paths, to prevent the application or" the control energy thereto, causing said energy transmitted for the production or" the desired over-all eect, it travels over said transmitting end, to control the transmission over said first and second paths at that end of the system, and rendering the transmission over said transmitting end of the path immune to interruption by the application to the system or the withdrawal therefrom oi control energy designed to pass over said second path,

7. ln a two-Way signal transmission system, including two paths adapted for transmission in opposite directions, means associated With each path for applying control energy thereto when such path is not being used for signal transmission, means associated with each path and responsive to said control energy for maintaining the path inoperative for signal transmission, means responsive to the application of signal energy to either path for interrupting the application of control energy thereto, and means associated with the transmitting end of one of said paths and responsive to signal energy therein for controlling the transmission thereover, said last mentioned means being independent of the application to the system or the Withdrawal therefrom of control energy designed to pass over the opposite path.

8. In a two-Way signal transmission system, including two paths adapted for transmission in opposite directions, means associated with each path i for applying control energy thereto when such path is not being used for signal transmission, means associated with the receiving end o each path and responsive to said control energyv for maintaining the path inoperative for signal transmission, meansresponsive to the application of' signal energy to either path for interrupting the application of control energy thereto and means associated With the transmitting end of one of said paths and responsive to signal energy therein for controlling the transmission thereover and over the receiving end of the opposite path, said last mentioned means being independent of the application to the system or the withdrawal therefrom of control energy designed to pass over the opposite path.

9. In a two-Way signal transmission system, including two paths adapted for transmission in opposite directions, means associated with each path for applying control energy thereto when such path is not being used for signal transmission, means associated with each of said control energy applying means for preventing the application of transients in the signal frequency range to the transmission path as a result of the operation of said control energy applying means, means associated with each path and responsive to said control energy for maintaining thepath inoperative for signal transmission, means responsive to the application of signal energy to either path for interrupting the application of control energy thereto, and means associated with the transmitting end of one or said paths and responsive to signal energy therein for controlling the transmission thereover, said last-mentioned means being independent of the application to the system or the Withdrawal tL ereirorn of control energy designed to pass over the opposite path.

lo. In a two-Way signal transmission system, including two paths adapted for transmission in opposite directions, means associated with each path for applying control energy thereto when such path is not being used for signal transmission, means associated with each of said control energy applying means for preventing the application of transients in the signal frequency range to the transmission path as a result of the operation of said control energy applying means, means associated With the receiving end' of each path and responsive to said control energy for maintaining the path inoperative for signal transmission, means responsive to the application of signal energy to either path for interrupting the application of control energy thereto, and means associated with the transmitting end of one of said paths and responsive to signal energy therein for controlling the transmission thereover and over the receiving end of the opposite path, said last-mentioned means being independent of the application t the system or the Withdrawal therefrom of control energy designed to pass over said opposite path.

EDMUND R. TAYLOR. DOREN MITCHELL.

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