US1995181A

US1995181A - Multiplex receiving apparatus

Info

Publication number: US1995181A
Application number: US658620A
Authority: US
Inventors: Kahn Alfred
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1933-02-25
Filing date: 1933-02-25
Publication date: 1935-03-19
Anticipated expiration: 1952-03-19
Also published as: FR768229A

Description

Patented Mar. 19, 1935 MULTIPLEX RECEIVING APPARATUS Alfred Kahn, Ozone Park, N. Y.,'assignor to Radio Corporation of America, a corporation of Delaware This invention relates to multiplex telegraph receiving systems, and has for its principal object to provide, in such a system, a method of and apparatus for easily and eiiiciently assigning the received signals to the diierent channels. More specically, an object is to provide a receiving system which is simple in construction, easy to maintain and which requires a mininum number of parts. y

The present invention, although 'not limited thereto, finds particular application to multiplex systems of the time division type, and for this reason the invention will be described with special regard thereto. In multiplex systems of the time division type the successive-basic units of each channel are divided into equal portions of like number as the several channels, and the transmittingI circuit is assignedl consecutively to successive channels for a time interval Aequal at most to one of these portions, the remaining portion of each basic unit of each channel being discarded and subsequently restored at thereceiving end of the circuit. Such a multiplex arrangement is described in United States Patent No. 1,979,484, granted November 6, 1934, to R. E. Mathes.

In brief, the present invention comprises a coupling system for assigning the received incoming signals to their respective channels, and for enabling the received signals to be rebuilt to their original form as at the transmitting station', whereby the suppressed portions of the transmitted signals are restored. For eecting this purpose, use is made of a coupling electron discharge device whose normal condition of electrical stability is changed upon the iiow of signal currents -in the input circuit of the receiving arrangement.

Referring to the single drawing accompanying this specification, there is shown a receiving circuit arrangement for a multiplex system in accordance with the present invention. This 4arrangement comprises, essentially, an energy collector or antenna 1, an ,amplifier and detector circuit 2 adapted to receive radio frequency energy from the antenna and to "'detect same in a manner Well known in the art, a tone keyer 3 under control Q f apparatus 2 for transmitting over a land line 4 to the -receiving station A audible frequency tone which is interrupted in accordance with received signal energy, an amplier and rectier circuit 5 for producing the envelope of the keyed tone, coupling tube 6 and a so-called kicker arrangement 7 with associated apparatusv for assigning the incoming signals to their re- Appliation `February z5, 1933, serial No. 658,620

c claims. 101. 17a-50) spective channels, each of the channels having -a locking circuit 8 for rebuilding the received ent No. 1,874,866, granted to I-I. H. Beverage, et v al., particularly jthat portion which relates to Figure 2 thereof.

Similarly, ampliner-detector apparatus 5, which also is of a well known type, has been indicated in box form, the output or full wave rectifier part only being shown in order to' illustrate its manner of connection to the coupling tube 6. Only the negative pulses of the rectified signal are applied to the grid of tube 6 since the positive end of the rectifier is tied down to. the filament which is at ground or zero potential. A low pass filter 9 consisting of series inductance and shunt capacitance is utilized for smoothing out whatever tone components remain in the rectified signal.

In the circuit diagram shown, coupling tube 6 is biased bymeans of a grid battery 10 to pass current normally, in which cndition there exists a positive potential on its anode which is lower in v'alue than the potential of the anode supply -l-Eb, due to the IR drop in resistance 11. The receipt of a signal pulse on the grid of tube 6, however, is arranged to bias the grid so negatively as to make the tube block, that is, cease passing current, at which time the voltage on the anode of tube 6 will rise to the maximum value of +En, since at this time no current ilowsv in the resistance 11.

Although this particular manner of operating tube 6 has beendescribed, it will readily be understood that the invention is not limited thereto, since the desired coupling effect canbe obtained in other Ways, for example, by biasing tube 6 to cut-off at all times except when a signal is impressed on its grid, merely by the use of a reversing tube, or else by permitting tube 6 to draw current at all times'and changing the magnitude thereof in accerdancewith the incoming signals.

For assigning the incoming signals to their respective channels, there is provided a rotating kicker disc 7 which may consist of any suitable distributor arrangement for conductively closing an electrical circuit between the output of coupling tube 6 and the different channels in succession. It is preferred, however, to use a commutator of the type described in United States Patent 1,963,587, granted June 19, 1934, to R. E. Mathes. In the particular arrangement shown,

\disc 7,. comprises an insulating drum having attached to its periphery metallic wipers or brushes 12 which are arranged, as they revolve, to momentarily bridge, in succession, a plurality of pairs of contacts 13, 14, and thus close a circuit from tube 6, which is associated with all of the contacts 13, to the respective channels which are individually connected through condensers 15 to the diierent contacts 14. Only two channels have been shown, but it will be understood that any desired number may be used. Kicker disc 7 is driven by a motor, not shown, which is maintained in synchronism by the incoming signals. Although any well known method of synchronism may be utilized it is preferred to employ the system described in a'copending application of R. E..

Mathes, Serial No.' 645,171, filed December 1, 1932.

In each receiving channel and in circuit with its respective condenser 15 is a locking circuit 8 for restoring the receiving signalsto their original form as they appeared before transmission. Since the locking circuit apparatus in each channel is the same, for the sake of simplicity, only a single channel circuit has been shown and will be described herein. The locking lcircuit comprises ltwo electron discharge devices 16, 17 which are arranged to, have two degrees of electrical stability. These tubes are unstable when both are drawing current, but stable when one ltube is passing current and the other blocking. The changing from one condition of stable equilibrium, such as when tube 16 is blocking and tube 17 is passing, to the other condition, when tube 16 is passing and tube 17 blocking, or the reverse, is caused by the presence of a suitable potential on the grid of tube 16 which is, due, in this case, to `a. charge on condenser 15, the latter, in turn, being in circuit with a

resistance

1,1 connected to the anode of tube 6, Vand a resistance.19 in the grid circuit of tube 16 of the locking circuit. This locking circuit is more adequately described in UnitedStates Patent 1,844,950 granted February 16, 1932 to J. L. Finch to which reference is made for a more detailed explanation of the operation thereof.

Coupled to the output terminals of the locking I circuit 8 may be any type of utilization circuit key an audible tone for transmission over land line 4 to the receiving station A at which the interrupted tone signals, corresponding to the incoming messages, are rectified and the envelope of the signals applied to the grid of tube 6. Filter 9 is used to smooth out any of the tone components remaining in therectiiied signal. The application of the rectified signals on the grid of tube 6 drives the grid negative and causes the current will flow through resistance` 11, and the plate will be at its maximum positive potential. The kicker 7, which is driven in synchronism with the incoming signal, will now'close the circuit from the anode of tube 6 through contacts 13 and 14, over brush or pin 12, to the condenser 15, thus charging the condenser. The application of this charge to condenser 15 causes a mornentary :dow of charging current4 into the condenser through a circuit including anode resistance 11 and grid resistor 19 of the locking circuit, thus enabling the application of a pulse of such polarity to the grid end of resistance 19 which will drive the grid of tube 16 positive. Tube 16 will now draw current, and due to -the characteristics of the locking circuit 8, tube 17 will be blocked. An electrical pulse of a predetermined polarity will thus be transmitted to utilization'means 18 over lead 20. This pulse will continue untiLthe conditions of tubes 16 and 17 of the locking circuit reverse, at which time tube 16 will block and tub e 17 pass current over lead 21 vto the utilization circuit.

Now, if at the next time the channel under consideration is assigned to the coupling circuit a signal is again being impressed on the gridof the coupling tube 6, condenser 15 will remain charged and tube 16 of the locking circuit will continue' to pass current. However, if at the time the channel is assigned to the circuit no signal is impressed on the grid of coupling tube 6, then anode current will iiow again through resistance 11 and will cause a drop of potential thereacross at the instant the contacts 13 and 14 are bridged by brush 12 of the kicker 7. Condenser 15 will now discharge over a path traced from Ea grid resistor 19, through contacts 13, 14 and wiper pin 12, and into tube 6, thus causing the grid end of resistance 19 to become negative and allowing tube 17 to pass current while tube 16 blocks. In this manner, there is obtained a push-pull output eiect which operates the utilization means, and reproduces the original signal characters transmitted, which may be of the Morse code or any other suitable type.

It will be understood, of course, from a mere inspection of the drawing vthat the invention is not limited to radio systems or to the precise arrangement of parts shown since land line systems may well be used and various modifications made in thecircuitsillustrated and described herein without departing from the spirit and scope of the appended claims.

1. A receiving circuit for a multiplex telegraph system comprising a rectifying system for rectifying the received signals and having an output circuit, an electron discharge coupling device associated with said outp'ut circuit, circuit closing means for connecting at predetermined intervals the output of said coupling device to the various channels, said device being arranged to change its normal condition of electrical stability upon the iiow of signal current in said rectifying system,` storage means in eachof said channels, the state of which is dependent upon the condition of said electron discharge device at the instant said device is connected through said circuit closing means to its associated channel, and utilization means individual to each channel under vthe control of said storage means.

2.. A receiving circuit for a multiplex telegraph system comprising a rectifying system for rectifying the received signals and having an output circuit, an electron discharge coupling device normally biased above cut-off to pass current associated with said output circuit, said device being arranged to become temporarily biased below cut-off upon the ow of signal current in said rectifying system, storage means, circuit closing means for connecting the output of said electron discharge device at predetermined intervals to said storage means, and utilization means in circuit with said storage means.

3. A receiving circuit for a multiplex telegraph system comprising a rectifying system for rectiying the received signals and having an output circuit, an electron discharge coupling device normally biased above cut-oi to pass current associated with said output circuit, said device being arranged to become temporarily biased below cutoff upon the flow of signal current in said rectifying system, a condenser, means for connecting the output circuit of said electron discharge device at predetermined intervals to said condenser, and utilization means in circuit with said condenser.

4. A receiving system for a multiplex telegraph system comprising a rectifying system for rectifying the received signals and having an output circuit, an electron discharge coupling device normally biased above cut-off to pass current associated with said output circuit, said device being varranged to become temporarily biased below cut-off upon the flow of signal current in said rectifying system, storage means, circuit closing means for connecting the output circuit of said electron discharge device at predetermined intervals to said storage means, a signal rebuilding system under control of said storage means comprising a plurality of electron discharge devices whose anodes and control electrodes are respectively interconnected, and a utilization circuit connected to said signal rebuilding system.

5. A receiving circuit for a multiplex telegraph system comprising a rectifying system for rectifying the received signals and having an output circuit, an electron discharge coupling device normally biased above cut-off to pass current associated with said output circuit, said device being arranged to become temporarily biased below cut-oi-upon the flow of signal current in said rectifying system, a condenser individual to each channel of the telegraph system, circuit closing means for connecting the output 'circuit of said electron discharge device at predetermined intervals to each of said condensers, signal rebuilding systems under control of said condensers comprising a plurality of electron discharge devices whose anodes and control electrodes are respectively inter-connected, and a utilization circuit coupled to each of said signal rebuilding systems.

6. A receiving system for a multiplex telegraph system comprising a rectifying system for rectifying the received signals and having an output circuit, an electron discharge coupling device normally biased above cut-off to pass current connected to said output circuit, a connection from the anode of said electron discharge device to a source of positive potential, a resistance in said connection, a pair of contacts one of which is directly connected to said anode and the other of which is connected to a terminal of a condenser, circuit closing means for conductively connecting at predetermined intervals said pair of contacts, a signal rebuilding system connected to the other terminal of said condenser comprising a plurality of electron discharge devices whose anodes and control electrodes are respectively inter-con-- nected, and a utilization circuit coupled to said signal rebuilding system.

ALFRED KAI-IN.