US1906775A - Voice operated gain adjuster - Google Patents

Description

May 2, 1933. E. M. STAPLES VOICE OPERATED GAIN ADJUSTERl Filed Dec. 23, 1931 FTS INVENToR EMS/@laks Bv ATTORNEY Patented` -May 2,- 1933 f VUNITEDST.1\fr1:s

PATENT. ,j

ELLIOT M. s'rArnEs, oF HoHoxUs NEW JERSEY, `AssIciNoR TOY-AMERICAN TELEI- PHONEAND TELEGRAPH COMPANY-,:AcoRPoRATIoNaoE NEW vom:Y .j y

voIcE OPERATED GAINpADJUsTER Ap-Plriaatmn mea December y2s, 1931. semina.. 582,896.;

. Among the objects ofmy inventionis to .provide a Vnew and improved method and` corresponding apparatus for adjusting the gain of an amplifier in a signal transmitting `5 system. Anotherfobject of iny'invention is to provide foradjusting theegain in accordance with the frequency of occurrence'.- of voltage peaks. Still. another object is to count voltagefpeaks on the output side of an amplifierl and adjust the input thereto so as keep the number of suchpeaks as nearly as practicable in yconstant ratio -to elapsed time. All these objects and various other objects and advantages of my, invention will become` apparent on consideration of the following disclosure V.of a specific example of practice in accordance with .the invention. `It will be understood that the following .disclosure relates principally to this particular examf ple ofmy invention and-that itsscope will be indicated inthe appended claims.

Referring to the drawing, this is a diagram of an amplifier and associated apparatus with which my invention may*v be practiced.

The amplifier k14 lies between the pair of input terminals 11, 12 andthe pair of output terminals 15, 16. Apotentiometer `13 isy introduced on the input side and it will readily be seen that by adjustment ofthe arm of the switch B, stepsof'resistance-are transferred from series to shunt and vice versa. f

The detector 18' is connected .across the 35 line through the switches 19`on the output side of the amplier 14. This detector 18-isj .adjusted so Athat any currents on the line above a certain low level will cause enoughr current to How through the relayC to close input side, that is in its grid circuit, is

adjusted so that at a certaindesired voltage the `tube will flash over, that is give a sudden'current rush in the plate circuit containingthe relay 22, This relayis slow acting.` It and likewise the other relays presently -to require V0.2'second to operate and 0.3 ,secondA to release.V When the flash-over currentA in the ouput circuit of the gas tube 21 operates j the relay 22,.it opens its own circuit at23 'co I the' right.` The release relay 29 steps this arm one step to the left, but release relay 25-25 returns' the-arm 24 all the wayV to n thev leftk even if relay 22 is operated. The switch arm 26y is driven by a motor or clock so as to makeone revolution in 5 seconds. At one pointin each revolution it makes contact withthe grounded metallic segment 27( for a period long enough to operatek relays 28or29. f y p Further details of structure will'become apparent., in connection with the following description ofthe operation'of the system. 'JUase' 1..-As willbe seen when all casesV havezbeenl considered-arm 24 lwillY be left on the 0l point immediately after arm 26 engages segment 27. Suppose that-during a single rotation of the arm 26 from 27 around again yto 27 there'is one and only one'voltage peak in the plate circuit of the gasvtube 21 of suiiicient intensity to operate relay 22. This single operation of the relay 22 willstepthe arm24: of switch A from `its `0 point to point 1,-where itwill remain .untilV the arm. 26 again reaches the segment 27 Thereupon a'circuit will be closed from ground throughv segment n 27, arm 26, front contact of 'relay `C,winding 25 of relay 25-25, point 1 oflswitch A, arm 24v and battery to ground.y The corresponding im'- pulse of currentin the circuit just traced, energizing the relay .25-25, will. return the switch arm24 toits O point.l .In this lcase no, adjustment of the potentiometer switch B will be made, andv aslong as there.:

is a recurrence of one and only one effective voltage peak per 5 second interval, no adjustment will be made at B. Each time the switch arm 24 will step from its 0 point 5 to point l and then at the end of the 5 second interval drop back to its point. One such voltage peak per second interval is considered to indicate a proper gain adjustn ment of the amplier 14.

Oase {If-Suppose that during such a 5 second period of rotation of the switch arm 26 from the segment 27 around and back to the segment 27 there is no voltage peak sufhcient to operate the relay 22 in the output circuit of the gas tube 2l. Then `the arm 24 will remain on the 0 point of the switch A, and when the arm 26 arrives at the segment 27 at the end of the 5 second period a circuit will be closed as follows:

From ground through segment 27, arm 26, front contact of relay C, release relay 29,

Y 0 point of switch A, its arm 24, and through battery to ground; The corresponding current impulse in the relay 29 will step the arm of switch B one step to the left, thus transferring a step of resistance 13 from series to shunt and increasing the intensity of the amplifier input, that is increasingthe over-all gain. Each time that a 5 second 30 interval passes without an effective voltage peak, the arm of the switch B will be stepped one point to the left until it reaches the end of its possible travel in that direction, putting all the resistance in shunt and none in 3.5 in series. The absence of a voltage peak in a 5 second interval is deemed to indicate that the amplifier 14 is not giving enough gaip and the adjustment is made accord- 1n t(ase I I I .-Suppose that during a 5 second interval, as determined by the rotation of the switch arm 26 from segment 27 around again to segment 27, there are two or more effective voltage peaks; thus, the arm 24 of switch A will he stepped twice to the right and will rest on point 2 when the arm 26 arrives at the segment 27. Thereupon a circuit will be closed from ground through segment 27, arm 26, front contact of relay 5U C, relay 28, point 2 of switch A, its arm 24,

and through battery to ground. The corresponding current impulse in the relay 28 will step the arm of switch B one step to the right, thus transferring a step of resistance from shunt to series and thereby decreasing the over-all gain of the amplifier 14. It is considered that if effective voltage `peaks occur as often as twice in a 5 second interval, this means that the amplifier gain is too high and requires an adjustment downward. The energization of the relay 28 also closes a Contact at 30, thus putting battery to a circuit through the winding 25 of relay 25-25 Vwhich restores the arm 24 of switch 65 A to its 0 point.

Briefly summarized, the operation involves increasing the gain, or leaving it unchanged, or decreasing it according as the number of effective voltage peaks is none per 5 second period, or one, or more than one. If there is over-adjustment one way due to fortuitous scarcity or frequency of voltage peaks in a 5 second period, it will be quickly corrected the other way in ensuing 5 second intervals. On an average, that is in the long run, 'the potentiometer 'i3 will be heldr at such adjustment that voltage peaks will occur at the rate of once per 5 second interval.

The detector 18 as connected in the system prevents adjustment when there are no voice currents on the line. lt can be omitted by opening the switches 19 and shifting the switch 20. lVhen it is omitted in this way and there is no speech on the line, then there will be an absence of voltage peaks and in each 5 second period there will be an adjustment described above for Case II, so that eventually the amplifier 14 will be adjusted for the utmost gain. .Then when speech starts, the necessary steps of adjustmentdown will quickly be made to bring the arnplilier output to the proper level.

That is claimed is:

l, The method of adjusting for gain which consists in counting voltage peaks above a certain degree of intensity, holding the gain unchanged when these peaks occur at a certain time rate, increasing' the gain when they occur less frequently, and decreasing the gain when they occur more frequently.

2. The method of adjusting for gain which consists in holding the gain unchanged when a voltage peak of as much as a certain degree of intensity occurs once in each of certain successive equal intervals of time, increasing the gain a step when no such peak occurs in such a period, and de creasing the gain a step when more than one such peak occurs in such a period.

3. The method of holding a certain desired power level at a certain point of a transmission line which consists in making gain adjustments in steps, with an added step when no voltage peak above a certain intensity occurs at that point within a certain period of time, with no step either way when there is one such voltage peak in said period, and with a subtracted step when there are more than one such peak in said period.

4. The method of adjusting for gain which consists in keeping the adjustment unchanged when voltage peaks above a certain degree of intensity occur at a certain rate and adjusting to increase or decrease the gain when these peaks are respectively less frequent or more frequent.

5. An amplifier adjustable for gain, a device responsive to voltage peaks above a certain degree of intensity .in the amplifier output, and a connectiontherefrom to adjust the amplifier, said connection comprising time lapse means to 'make adjustment dependent on frequency of response of the said device. f

6. An amplifier, means to adjust itsgain in steps, a device responsiveto voltage peaks above-a certain degree of intensity on rits output side, a relay controlled accordingly by said device, a motor driven commutator,k and means controlled jointly by said relay and commutator to adjust said first mentioned means for gain according to the relan tive frequency of occurrence of the voltage peaks.

7. An amplifier, means to adjust it for gain, a deviceconnected on its output side and responsive to voltage peaks above a certain intensity, a counting mechanism I to count such voltage.. peaks to 0, 1 kor 2, a motor driven commutator, and circuit vconnections to actuate said means for adjusting the amplifier according to the count in the counting mechanism and the completion of i,

a time cycle in the commutator.

In testimony whereof, I have signed myy name to this specification this 22nd day of December 1931.

ELLIOT'M. STAPLES.

Images