US2026696A - Signaling system - Google Patents

Description

D. MITCHELL SIGNALING SYSTEM Filed Dec. 29, 1935 Jan. 7, 1936.

ATTORNEY INVENTOR Mchte@ BY I A I I I f Y I I Y 7; l m N+ NMMNWEQ @www Nmwww mN+ III l II I I I I I I I I I I I Patented Jan. 7, 193.6

t UNITED sTATEs SIGNALING SYSTEM Doren Mitchell, Bound Brook, N. VJ., assigner to American Telephone and Telegraph Company, a corporation of New York Application December 29, 1933, Serial No. '104,557

35 claims. (c1. 17a- 44) Thisinvention relates to signaling systems, and more particularly to signaling systems in which either carrier energy orspecial control energy is applied to the transmitter only during the periods of signal transmission. With greater particularity, the invention relates to carrier systems of the type indicated in which the gain of the receiver is automatically controlled by the received carrier energy. An example of the systems to which the invention is applicable is a short-wave transoceanic radio system in which it is desirable that the carrier be removed when no signal energy is applied to the transmitter and that the receiver gain be controlled by the carrier energy. It is to be understood that the invention is equally applicable to systems in which the control is effected by a special frequency wave which is not the carrier.

In systems of the indicated type as operated heretofore, when the carrier (or other control energy) is removed from the transmitter, the receiver gain may rise by decibels or even a greater amount; when the carrier is again applied to the system, it becomes necessary to reduce the receiver gain before signal waves can be received without considerable distortion due to overloading. Since it is generally desirable to make the gain adjusting action relatively slow, in order to avoid excessive hunting in the gain control de- 'Vice and the resultant distortion, there may be a period of several seconds after the carrier is reapplied which is marked by the distortion of the signal due to the excessive gain of the receiver.

The principal object of the invention is to reduce as far as possible the distortion heretofore introduced in the receiver in connection with the removal of the carrier or other control energyand the subsequent re-application of that energy. Subordinate objects are to provide for a receiver 1 gain of a desirable value when the carrier isv removed and to provide for the quick readjustment of that gain when the carrierA is again received, possibly with a widely different value.

In general, the above-stated objects are attained by novel methods and means whereby, when the carrier or other control energy is removed, the receiver gain is either maintained at its last value or, if the carrier is off for a predetermined time, brought to some other predeter- 'mined valve, and, when that energyagain arrives, the receiver gain is quickly readjusted to the new carrier or other control energy intensity, without the delay which would normally be introduced by the slow action of the gain adjusting device.

The invention will be clearly understood when the following description of one desirable arrangement of the circuits and of the operation thereof is read with reference to the accompanying drawing, of which- Figure 1 shows schematically a signaling system in which thecarrier is applied at the transmitter only when signal energy is to be transmitted and in which the received carrier controls the receiver output path andv the receiver gain, and indicates the novel features introduced by the applicant;

' Fig. 2 shows diagrammatically a suitable arrangement of the receiver circuits; and

Fig. 3 shows diagrammatically a modification of the circuits of Fig. 2 to suit the case of control energy other than the carrier.

With reference to the schematic disclosure of Fig. 1, there is indicated a signaling system including a transmitting station W at the left and a receiving station E at the right. The system specifically indicated is a radio system but it will be understood that the transmission from station W tostation E might as well be over wires. When there is no signal to be transmitted, the oscillator is disassociated from the modulator at the transmitting station W. At the receiving station E, there is indicated a receiver having a demodulated signal path which may be controlled at a point b. When no signal is applied to the system,

this demodulated signal path is disabled at4 point b.

If signal is transmitted, energy is diverted at point a at the transmitting end and serves to connect the oscillator with the modulator. After being ampliiied and radiated from the station W, this energy is received at the station E. There areindicated schematically at the station E a codanthat is, a carrier operated device antinoiseand automatic gain control apparatus. When the carrier energy is received at the station E, energy istaken from the receiver circuit to y operate the codan and the automatic gain control circuit. The eifect of the operation of the codan is to remove the disability at point b and thus render the receiver output operative. It will be noted that normally the output of the automatic gain control is disassociated from the receiver. When, however, the carrier energy arrives, an operation at` point c serves to connect the output of the gain control with the receiver input. As is indicated by the condenser, provision is made, in accordance with the applicants invention, for some normal control of the receiver gain in the absence of the connection of.

the automatic gain control output with the ceiver input.

Thus, by the schematic showing of Fig. 1, there is indicated a signal system in which the carrier is applied at the transmitting end only under the control of the signal; when the carrier reaches the receiving end, the normally disabled demodulated signal path is rendered operative and the gain of the receiver is controlled by the incoming carrier. In the absence of the reception of carrier energy, however, a certain control. is exercised over the receiver gain.

In Fig. 2, there is shown diagrammatically and, in part, schematically, one desirable arrangement of the receiver circuits. It will. beV understood that the carrier energy is applied to the system and its application interrupted in the manner indicated in Fig. l. The pertinent portions of the complete receiver circuit are shown as a high frequency amplier, a first detector, an intermediate frequency ampliiier and lter, a second detector and an audio-frequency amplifier. The output of the audio-frequency amplifier or, in other words, a portionof the demodulated signal path is designated L. Those` portions of the complete circuit which make up the codan and the automatic gain control device are appropriately indicated. A relay chain comprises the codan relay S1, a relay S2, which may be called the gain-maintaining relay, and a relay S3, which is preferably slow-operating and slow releasing and may be called the quick gain control relay. It should be noted that the circuits are shown in the condition produced by the reception of carrier energy at the receiving station; accordingly, relays S1, S2 and Ss are in released condition and the path L is operative.

' The apparatus already mentioned', along with ..certain condensers, resistances and batteries,

make up the circuits arranged in accordance with the applicants invention, except that certain elements may be added in accordance with a modification to be described hereinafter. It is believed that the details of thev circuits will be best understood-from a reading of the following discussion of the operation.

Received carrier energy causes current to flow in the circuit ofthe second detector, which includes a resistance R1. WhenY current ows through resistance R1 toground, the grids of the two vacuum tubesT andT1, whichV are connected to resistance R1, become negative with respect to ground. In tube T, which forms a part of the codan circuitthe voltage on the grid is adjusted so that, with the reception'of carrier, it will be sumciently negative to reduce the plate current ofr tube T substantially to zero. Accordingly, relays S1 and S2 have no appreciable current in their windings and are in the released condition. The release of relay S1 removes the disability normally applied to the path L and incoming transmission is permitted to pass on over the receivingcircuits.

The release of relay S2, the gain-maintaining relay, connects ground through the left-hand armature to a resistance R6 associated with the condenser C1 of the gain-control circuit. This connection permits the normal action of the gaincontrol circuit while the carrier is being received; also the position of the left-hand armature of relay S2 causes relay S3, the quick gain control relay, to be released.

As indicated above, the voltage set up in resistance R1, when the carrier is received, acts on the automatic gain control circuit through tube T1. The negative voltage in the resistance tends to lower the current in tube T1 and thereby results in the lowering of the current in resistance R2 and the reduction of the negative voltage applied to` the grid of the tube T2. Thus, the 5 plate current of tube T2 tends to increase, with the resultant tendency to charge the condenser C1 through resistance R3, the upper side of the condenser being charged to a negative value with respect to ground. It will be understood that tubes T1 and T2 form a second stage of the gain control circuit, through which stage there is directly exercised an appropriate control of the grid voltages of the vacuum tubes constituting the high frequency amplier, the iirst detector and the intermediate frequency amplifier of the receiver proper. It will be understood further from the discussion already had and from an examination of the batteries included in the circuit that the arrangement disclosed tends to maintain a constant output of carrier from the second detector; if this output becomes too high, the increased negative voltage in resistance R1 results in the charging of condenser C1 and the increase of the negative voltage on the grids of the receiver tubes. If, on the other hand, the carrier output becomes too low, condenser C1 discharges through resistances R4 and Re and the left-hand armature of relay S2, and the negative bias on the receiver tube grids is reduced, with the result of an increased gain. Resistance R3 tends to slow down the charging of condenser C1 while resistances R4 and Re tend to delay the discharge of that condenser. The net result of the operation of this gain control circuit is that the carrier output of the second detector tends to remain constant.

If, now, the reception of carrier energy ceases, the current in resistance R1 drops to Zero, the negative bias on the grid of tube T is removed o and plate current flows in this tube and through the windings of' relays S1 and S2. The operation of relay S1 places a short circuit on the audiofrequency amplier output or path L and thus, in the absence of carrier and signal transmis- 5 sion, interfering energy cannot pass on over the receiving circuit.

When relay S2 operates its left-hand armature, ground is removed from resistance Rs and the I further discharge of condenser C1 is prevented.`50 This relay operation also connects ground to resistance R1 and a second condenser C2 starts to discharge through that resistance. This discharge, if continued, will cause the operation of the quick gain control relay S3. It will be noted 65 that the current through the winding of this relay is that produced by the difference between the voltage from the battery B1 associated with resistance R5 and the voltage of condenser C2. It A should be noted at this point that since, with the removal of the carrier and the operation of relay S2, the condenser C1 can no longer discharge, the gain of the receiver will be maintained at a substantially constant value, some slight allowance being made for the gradual leakage of the charge on condenser C1; in other words, the receiver gain is maintained at a predetermined value, that is at the setting last established by the operation resulting from the reception of the carrier energy.

As has been indicated hereinabove, it is desirable that the gain adjusting action be relatively slow in order to prevent excessive hunting of the gain control devices and the resultant distortion. Accordingly, when the carrier comes on again, it may be an appreciable, time before the receiverfgainwill be adjusted to prevent distortion, since the value 4,of there-applied carrierv may be widely dierentfrom that obtaining before the cessation of carrier reception. To avoid .this difficulty, the applicant provides for the abnormal, quick adjustment of the receiver gain when the carrier is again received. To accomplish this quick adjustment isthe function of the` relay S3. After the removal ofthe carrier and the effective discharge of condenser C2, relay S3 operates and placesa short circuit around resistances R3 Vand R4. Accordingly, when the carl rier again cornes on, the gain control circuit will quickly adjust the receiver .gain V to meet anyA change between the new carrier valueV and the old. As has been indicated above, relay Ss is made slow operating and slow releasing. The relay should operate slowly so that when the carrier is merely interrupted for a very short period instead of actuallybeing removed fora consid-.q

erable period, the gain control apparatus will function in the normal manner; the relay should release slowly so that when the carrier reappears after a substantial interval, the quick adjusting feature will be maintained long enough to permit` the receiver to become adjusted to the new carrier value. `After that Yfunction `has been performed, of course, relay S3 releases and the gain control circuit functions normally until after the carrier is again removed.

The action of the quick Vgain control relay S3 will now be considered in, further detail. The

" time actions o-f this relay .are affected by resistances R5 and R1 and the` condenser C2; When relay Sz first operates after an extended period of release, condenser l `Cz startsA 4to discharge through resistance `Rr. Previously, this condenser has been charged to thevalue of battery B1 associated with resistance R5. `If relay S2 is` operated only for a short period, the discharge of condenser C2 will be slight and the current flowing through resistance R5 andthe winding of relay S3 will be small, since, as stated above, this current depends on the difference between the voltage of battery B1 andthe charge on condenser Cz and relay S3 will not o-perate.V If relay Sz operates for a suicient time to discharge C2 as far as possible, however, the current in relay -Ss will be more than suicient to operate it.. Y The joint action of resistance R5 andV condenser C2 then serves to delay therelease Vof relay S3 for a sho-rt period after relay Sz releases.

It may be desirable in certain cases to have the receiver gain `set at some predetermined value other than the last value produced by the gain control circuit when the carrier is` removed for more than a predetermined time. It would probably not be desirable to set the receiver at its 'fixed gain when the carrier dropped out for only a short interval.V For such modified operation, there is added to the relay S2 a right-hand armature and, furthermore, a relay S4 andan adjustable battery B2 are added, along with resistances Re and R9 and condenser C3. .Relay S4 controls the connection of a battery Bz to resistance R6.` While carrier `is being received, the right-hand armature of relay S2 is against its contact and a circuit is completed through the winding of relay S4. As long as this condition obtains, thecircuit between battery B2 and resistance Re is broken..A If, however, the carrier is removed and the. armatures of relay S2 are, separated from'. their back` contacts, relay S4. eventually releases and battery B2 is connected through resistance Re to thecondenser C1 of the gain control circuit. The time required for relay S4 to release is controlled bythe time required forcondenser VC3 to be charged up through Rs and the winding of S4. Resistance R9 is corn- 5^ paratively small and .is used toprevent burning of the contacts oflvrelay S4. YWith the adjustment of battery B2, the receiver gain setting can thus be brought back to any suitable predeteri, mined value. The product RsXCs should be 1d greater thanRsXCz or R7 C2.

As has been stated hereinbefore, the applicants invention is Vapplicable not only to the case of vcontrol of thereceiving circuitsby the carrier but also to the case of such control by any other control energy of special frequency. In the later case, the receiverarrangement for controlling the voltage in resistance R1" may be modified to take the form indicated inlFig. 3, `in which the n, control energy taken from the output of the sec- 20 ond detector mustpass through a band-pass filter F and operate a rectifier tube RTbefore there is any effect on resistance R1. l It will be understood thatf once the effect is produced in resistance R1, the operation of thezcircuit as modified in ac- 25'V cordance with Fig. 3 follows that of the circuit of Fig. 2.

While the invention has been disclosed specifically for the purpose of illustration, it is to be Vunderstood that it may take many ,other and 30 widely diiferent forms within the spirit of the invention as defined by the appended claims.

What is claimed is:

1. In a system ,for the reception of signals, including a receiver'` and means responsiveto the 35 reception and non-'reception of distinctive energy for governing the receiver, the method of transmission control whichconsists in adjusting the gain of the receiver while the. governing ,energy is being received in accordance with the intensity 40 ofsaid energy, and in theabsence of said energy maintaining said gain at the value last established for a time not in excess of a predetermined period.

2. In a system for the reception. of signals, including a receiver and means responsive to the reception and non-reception of distinctive energy for governing the receiver, the method of transmission control which consists in adjusting the gain of the receiver while the governing energy is being received in accordance with the intensity of said energy, maintaining said gain at the value last established while the reception of said energy is absent for a predetermined or shorter time, and setting said gain at a predetermined value at the expiration of said predetermined time if `the absence of the governing energy continues.

3. In a system for the reception of signals, including a receiver and means responsive to the reception and non-reception of` distinctive energy 60' for governing the receiver, the method of transmission control which consists in adjusting the gain of the receiver while the governing energy is being received in accordance with the intensity of said energy, normally retarding the gain ad- 55 justing action, setting said gain at a suitable value in the absence of said energygand temporarily speeding up the gain adjusting action .after the absence of said energy has continued for a predetermined time.

4. In a system for the transmission of signals, including a transmitting station and a receiving station, the method of transmission control which consists in sending from the transmitting station during the periods of signal transmission control 15 20,., ergy is removedfor. a'considerabletime, and after i only during the periods of signal transmission,

energy of a, distinctive frequency, adiustingthe gain 'atA thefr eivrig.V station lwhilefsai'd; control energy is being vreceived inil accordance"y with the intensity of said energyl, lormallyretarding the ,Y gain adjusting action,"'maintainingv 'said' gain, during the periods `when, no' control 'energy isA being received, at the value 'last `-established, and temporarily speeding up. the gain adjusting action afterthre absenceoffthe contrl'energyhas continued for a predetermined time.

5. In a system Afor the transmission of signals, including a transmittingl station and a'receiving station, the method of transmission control which consists in sendingv from the transmittingv station during the periodsv of signal transmission control energy of a distinctive `Afrequency, adjusting the gain at the receivingstation While said control energy is being received in accordance with the intensity of said energy, maintaining said gain at the value last establishedif. the control enthe absence of the control energy has continued for a predetermined timejsetting' said gain at a predetermined value'.

6. In a system for the transmission of signals,

" including a transmitting station and a receiving station, the method of transmission control 4which consists in sending from the transmitting station control energy' of a distinctive frequency, ad-

justing the gain at the receiving vstation while said control lenergy is being received in accordance with the intensityfof said energy, maintaining said gain at the value lastestablishedfif the control energy ceases, for a considerable time, setting said r gain at a predetermined 'value after the control energy hsbeeh absent. fQl 1 redetemineid time, and quickly readjiistingsjaid gain when 'the control energyl is ren-applied tothe system..

7. In a 'system for" the' reception of signals, including a receiver and demodulated signal path associatedY therewith, the' methndof transmission control which consists in applying control energy of a distinctive frequency to the "system only during the periods of signal' transmission, providing for the adjustmentof the receiver ain while the control energy'is beingv received' in accordance maintaining said demodulated signal path in a condition of disability when said'control energy is not being received, causing the reception of said control energy to rendersaid path operative,

providing for the adjustment o f the receiver gain while the control energyis being received inv accordance with the intensity of said energy, setting said gain at a suitable value when the control energy is removed from the system for a considerable time, and quickly rendering said adjustment eilective when the control energy is reapplied to the system after a substantial interruption, even though the value of said energy has changed to a considerable degree.

were@ 9- In.A @Signaling syslemneludns a transmitting ,station anda'receiving station, means at'the transmitting station underthecontrol of the signal energy forapplying to the system control energyof a distinctive frequency, means at the receiving station controlled by the received controlenergy for regulating the gain of the receiver, means for normally retarding the action of the gain regulating means, means responsive to the cessation of the reception of said control energy for maintaining said gain attthe value last establishedyand means responsive to the absence of saidcontrol energy beyond a predetermined time for temporarily disabling the retarding means.

10. Inr a signaling system including a transmitting station and a receiving station, means at the transmittingstation under the control of thev signal energy for applying tothe system control energy of a distinctive frequency, means at the' receiving station controlled by the received control energy for regulating the gain of the receiver, means responsive to a cessation of the` reception of the control energy for maintaining said gainat the value last established, and means responsive to the absence of the control energy beyond a predetermined time for setting the receiver gain at a predetermined value.

11. In a signaling system including a transmitting station and a receiving station, means at the 'transmitting station under the control of the signal energy for applying to the system control energy of a distinctive frequency, means at the receiving station controlled by the received control energy for regulating the gain of the receiver, means responsive to the cessation of the reception of control energy for maintaining said gain at the value last established, means responsive to the absence of the control energy for longer than a predetermined time for setting said a demodulated signal path, said path being normally maintained in a condition of disability,

40k gainv at a predetermined value, and means for i" means at the transmitting station under the control of the signal energy for applying to the system control energy of a distinctive frequency,

means at the receiving station responsive to the reception of said control energy for removing the disability from said demodulated signal path, means at the receiving station controlled by said control energy for regulating the gain of the receiverv in accordance with the intensity of said energy, means for normally retarding the action of the gain regulating means, means for setting the receiver gain at a suitable value during the absence of thecontrol energy,'and means responsive to the absence of the control energy beyond a predetermined time for temporarily disabling the retarding means.

13. In a system for the reception of signals, including a receiver and a demodulated signal path associated therewith, the method of transmission control which consists in maintaining the demodulated signal path in a condition of disability when no carrier energy is being received, causing the reception of carrier energy to render said path operative, adjusting the gain of the receiver whilethe carrier energy is being received in accordance With the intensity of said energy, normally retarding the gain adjusting action, maintaining said vgain atthe value last established 'which' consists in maintaining the demodulatedV whenthe reception of carrier energy ceases, and

temporarily speeding up the gain adjusting ac- K tion after the absence of carrier energy has continued for a predetermined time. p

. 14. In a system for the receptionl of signals, including a receiver and a demodulatedsignal path associated therewith, the method of transmission control which consists in` adjusting the gain of the receiver whilecarrier energy is being received in accordance with the intensity of said energy, maintaining said gain at the value last established while the carrier energy is absent for a predetermined or shorter time, setting said gain ata predetermined value if the absence oi carrier energy continues beyondsaid predetermined time and quickly readjusting said .gain when said reception issrenewed. l,

' 15. In a system for the reception of carrier Venenergy to be modulated bysignals, including a receiver and ademodulated signal path associated therewith, the method of transmission control which consists in adjusting the gain of the receiver while carrier energy is being received in accordance with the intensity of said energy, and in the absence of said energy maintaining said gain at the value last establishedfor a time not in excess of a predetermined period.:

16. In a system for Athe reception of carrier energy to be modulated by signals, including a receiver and a demodulated signal path associated therewith, the method of transmission control which consists in adjusting the gain of ,thereceiver while carrier energy is being received in accordance with the intensity of said energynormally retarding the gain adjusting action, maintaining said gain at the value last established if the reception of the carrier energy is ,absentfor a time not in excess of `a predetermined period, and temporarily speeding up thegain adjusting action after the absence of` carrier energy has continued fora predetermined time. Y

' 17. In a system for the reception of carrier energy to be modulated by signals, including a receiver and a demodulated signal path associated therewith, the method `of transmission control which consists in maintaining the demodulated signal path in a condition of disability when no Y carrier energy is being received, causing the reception of carrier energy to render said path operative, .adjusting the 'gain of the receiver while thecarrier energy is being received in accordance with the intensity of said energy, and in the absence of said energy maintaining said gain at the value last established `for a time not in excess of a predetermined period.

18.In a system for the reception of signals, including a receiver and a demodulated signal path associated therewith, the method` of transmission `control which consists in maintaining the demodulated Vsignalpath in a `condition of d isabilitywhen no carrier energy is being received, causing the reception of carrier energy to render said path operative,. adjusting the gain of the receiver while the carrier energy is being received in accordance with the intensity of said energy, maintaining saidgain at the value last established while the carrier energy is absent for a predetermined or shorter time, Vand settingsaid gain at a predetermined value if the absence of carrier energy continues beyond said predetermined time. l. l

19. In a system for the` reception of carrier energy to be modulated by signals, including a receiver and a demodulated signal path associated 5 therewith, the method of transmission control signal path in a condition of `disability when no carrier energy is being received,.causing thereception of carrier energy to render said path operative, adjusting the'gain-of the receiver while the carrier energy is being received in accordance withtheintensityof said energy; normally retarding the gain adjusting action, in the absence of the carrier energy maintaining said gain at the value last established ior a time` not in excess of a predetermined period, setting said gain at a predetermined value if; the absence'o carrier energy continues beyond' said predetermined period, and temporarily speeding up the gain adjusting action after the absence 4of the carrier energy has continued for a predetermined time.

20; In a system for the reception of carrier energy to be modulated by signals, including a receiver and a demodulated signal path associated v has greatly changed.

21.In a system forthe reception of carrier D energy to be modulated bysignals, including a receiver and a demodulated signalpath associated therewithythe method of-transmission control which consists in providing for the adjustment of the receiver gain 4while carrier` energy is being received in accordance with the intensity of said energy, normally retarding the gain adjusting action, setting said gain at a suitable value in the absence of carrier energy, and itemporarily speeding up the gain adjusting action after the absence of carrier energy has continued for `a predetermined time.

22. Inasystem for thereception of acarrier wave to be modulated by signal energy, a receiver having a demodulated signal path associated therewith, means controlled by carrier energy transmitted to the receiver for regulating the gain of the receiver, and means responsive to the cessation of the reception ofcarrier energy for maintaining said gain atthe value last established for a time not in excess of a predetermined period.

23. In a system for the receptionl of a carrier wave to be modulated by signal energy, a receiver having a, demodulated signal path associated therewith, means controlled by carrier energy transmitted to the receiver for regulatingthe gain of the receiver, means for normally retarding the action of the gain regulating means, means responsive to the cessation of the reception of carrier energy for maintaining said gain at the value last established, and means responsive to the absence of carrier, energy beyond a predetermined time for temporarily disabling the l retarding means.

the absence of carrier energy continued beyond said predetermined time for setting said gain at a predetermined value.

25. In a system for the reception of a carrier Wave to be modulated by signal energy, a receiver having a demodulated signal path normally maintained in a condition of disability, means responsive to carrier energy transmitted to the receiver for removing the disability from said path, means controlled by said carrier energy for regulating the gain of the receiver in accordance with the intensity of said energy, means for normally retarding the action of the gain regulating means, means responsive to the cessation of the reception of carrier energy for maintaining said gain at the value last established, and means responsive to the` absence of carrier energy beyond a predetermined time for temporarily disabling the retarding means.

26. In a system for the reception of signal energy, a receiver having a demodulated signal path normally maintained in a condition of disability, means responsive tocarrier energy transmitted to thereceiver for removing the disability from said path, means controlled by said carrier energy for regulating the gain of the receiver in accordance with the intensity of said energy, means responsive to the cessation of the reception of carrier energy for maintaining saidgain at the value last established, means responsive to the continuation ofthe absence of the carrier energy beyond a predetermined time for setting said gain at a predetermined value, and means for quickly readjusting said. gain when the reception of carrier energy is renewed. Y

27. In a system for the 'reception of a carrier wave to be modulated by signal energy, a receiver having a demodulated signal path associated therewith, means controlled by carrier energy transmitted to the receiver for regulating the gain of the receiver in accordance with the intensity of said energy, means'for normally retarding the actionof the gain-regulating means, and means responsive to the absence of carrier energy beyond a predetermined 'time for temporarily disabling the retarding means.

28. In a system for the reception of a carrier wave to be modulated by signal energy, a receiver having a demodulated signal path associated therewith, means controlled'byl carrier energy transmitted to the receiver for regulating the gain of the receiver in accordance with the intensity of saidk energy, and means responsive to the cessation of the reception of carrier energy for maintaining said gain at the value last established for a time notin excess of a predetermined period.

29. In a system for the reception of a carrier wave to be modulated by signal energy, a receiver having a demodulated signal path normally maintained in a condition of disability, means responsive to carrier energy transmitted to the receiver for removing the disability from said path, means controlled by said carrier energy for regulating the gain of the receiver in accordance with the intensity of said energy, and means responsive to the cessation of the reception of carrier energy for maintaining said gain at the value last established for a time not in excess of a predetermined period.

30. In a signaling system, a transmitting station, a receiving station including a receiver and a demodulated signal path, means at the transmitting station under the control of the signal energyfor applyingcarrier energy tothe system,

means at the receiving station controlled by the received carrier energy' for regulating the gain `of the receiver, and means responsive to the cessation of the reception of carrier energy for maintaining said gain at the value last established for a time not in excess of a predetermined period.

31. In 'a signaling system, a transmitting station, a receiving station including a receiver and a demodulated signal path, said path being nor- 10 mally maintained in a condition of disability. means at the transmitting station under the control of the signal energy for applying carrier energy to the system, means at the receiving station responsive to received carrier energy for removing the disability from said demodulated signal path, means at the receiving station controlled by said carrier energy for regulating the gain of the receiver in accordance with the intensity of said energy, means for maintaining the receiver gain at the last established value when the reception of the carrier energy ceases, means responsive to the absence of thecarrier energy continued beyond a predetermined time for setting said gain at a predetermined value, and means for quickly readjusting said gain when the reception of the carrier energy is renewed.

32. In a receiver of signal energy, means responsive to incoming energy for regulating the gain of the receiver, means for normally retarding the action of the gain regulating means, and means responsive to the absence or incoming energy beyond a predetermined time for temporarily disabling the retarding means, whereby the subsequent renewal of the incoming energy will produce immediate readjustment of the gain of the receiver.

33. In a receiver of signal energy, means responsive to incoming energy for regulating the gain of the receiver, means for normally retarding the action of the gain regulating means, means responsive to the cessation of incoming energy for setting the gain of the receiver at a suitable value, and means responsive to the absence of incoming energy beyond a predetermined 45 time for temporarily disabling the retarding means, whereby the subsequent renewal of the incoming energy will produce immediatevreadjustment of the gain of V.the receiver.

34. In a receiver of signal energy, the method of transmission control which consists in adjusting the gain of the receiver in accordance with the intensity of incoming energy, normally retarding the gain adjusting action,and providing for the temporary withdrawal of the retardation of the gain adjusting actionv after the absence of incoming energy has continued for a predetermined time, whereby the subsequent renewal of the incoming energy will produce immediate readjustment of the gain of -thereceiven 35. In a receiver of signalenergythe method of transmission control which consistsin adjusting the gain of the receiver in accordance-with'the intensity of incoming energy, normally retarding the gain adjusting action, setting the gain of thereceiver ata suitable value in the absence' of incoming energy, and providing for the temporary withdrawal'of the retardation of the gain adjusting action after the'absence of incoming energy has continuedfor a predetermined time, whereby the subsequent renewal of the incoming energy will produce immediate` readjustment of the gain of the receiver,

DOREN MITCHELL.

Images