AN-GRA-71_coder-burst_transmission_serv_TM11-5835-224-35_1969.pdf

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1、r T M 1 1 - 5 8 3 5 - 2 2 4 - 3 5 D E PA R T M E N T O F T H E A R M Y T E C H N I C A L M A N U A L I I r* DS, GS, AND DEPOT MAINTENANCE MANUAL INCLUDING REP AIR P ARTS AND SPECIAL TOOL LISTS CODER-BURST TRANSMISSION GROUP AN/GRA-71 r HEADQUARTERS, DEPARTMENT JULY 1969 O F T H EARMY CAUTION Before

2、taking resistance measurements on the transistorized circuits of the KE- the other row corresponds to the dashes in the character. A detent device (indexing roller) aligns and holds the coding wheel in position during record ing of a character. 1-9. Dot and Dash Coding Assemblies The dot and dash co

3、ding assemblies are used to sense and convert the mechanical pattern of holes in the coding wheel into a pattern of elec trical impulses to be recorded on magnetic tape. In this capacity, the coding assemojies drive the spacing mechanism, the impulse generator, ana the dot and dash switching assembl

4、ies. Each cod ing assembly consists of four sensing pins, six coding levers (some are not used), four or fi ve coding cams, coding lever bail, switch-and-bell- crank actuator, bellcrank, and a stroking fi nger. Essentially, a dot or dash is detected when a sensing pin enters a hole in the coding whe

5、el. This action causes a coding lever to pivot, the coding lever bail to engage, and the switch-and- bellcrank actuator to close a switch to the dot or dash track on the recording head. As the actuator closes the switch, it also positions a stroking fi nger to engage a spacing universal bar; the imp

6、ulse generator is then actuated, which causes a current impulse to be delivered to the dot or dash track on the recording head. The stroking fi nger is then brought down, en gaging the spacing universal bar. and the tape is advanced. 1-10. Impulse Generator (CO/B-8 Coder) The impulse generator is th

7、e electrical power- plant or the CO/B-8 coder. It consists of a permanent-magnet structure with a fl at, spring steel armature surrounded by a coil. Whenever the armature is stroked by the impulse generator actuating cam (attached to the dot coding cam shaft), its vibration causes an impulse of curr

8、ent to fl ow in the coil winding. The current impulse is delivered to a half-wave rectifi er, consisting of a series diode-resistor combination which clips off the positive portion of the alternating current (ac) wave and delivers only a negative impulse to the switching assemblies. The ac out put o

9、f the generator must be rectifi ed, because ac will not place an impulse on the tape. 1-11. Dot and Dash Switching Assemblies (CO/B-8) The negative current impulse from the generator is switched to either the dot or dash track wind ing on the dual-track recording head by means cf two single-pole, do

10、uble-throw (spdt) switches that comprise the switching assemblies. These switches are actuated iby their resjpective swdtch- and-JbeillKiranik actuators whenever a hoile is de tected by a sensing pin. Normally, these switches ground the head windings when they are not in use to prevent stray pickup

11、from being recorded. 1-3 TM 11583!5-224-35 When either switch is engaged by its respective switch-and-bellcrank actuator, it opens the groundpath and connects its respective head track to the impulse generator in anticipation of the current impulse. 1-12. Recording Head (CO/B-8) Whenever an impulse

12、of current passes through either winding on the recording head, iron oxide particles embedded in the magnetic tape are magnetically polarized. This magnetic polariza tion creates a magnetic impulse on the tape which produces the actual recording process. 1-13. Spacing Mechanism (CO/B-8) The spacing

13、mechanism is used for proper tape advance of dots, dashes, character spaces, and word spaces. The advancing mechanism is con trolled by the dash spacing universal bar. As this bar is depressed, it engages a feed pawl and causes the pawl to advance a feed ratchet one or two teeth. For dashes and word

14、 spaces the dash spacing universal bar is depressed to its limit to allow a two-tooth movement of the pawl, and for dots it is partially depressed (by the dot spacing universal bar) to allow only a one- tooth movement. 1-14. Sequence of Functioning (CO/B8) a. When a character is selected on the char

15、ac ter dial, its Morse hole-pattern on the coding wheel is moved into coding position directly over the dot and dash sensing pins. If the character contains dots, holes will appear above the appro priate dot sensing pins; if the character contains dashes, holes will appear above the appropriate dash

16、 sensing pins. b. As the operating handle is pulled, cam shafts in the dot and dash coding assemblies ro tate. Attached to each camshaft is a set of cams (under the coding levers) with their recessed edges displaced 60 apart. Spring-loaded coding levers ride the cams on each assembly, and each lever

17、 pivots in sequence as the camshaft rotates through 360. As each lever pivots, it lifts the sensing pin up to the coding wheel so that a dot sensing pin and a dash sensing pin rise as a pair, with each 60 rotation of the camshafts. If a sensing pin fi nds a hole in the coding wheel, it passes throug

18、h the hole and a dot or dash is recorded. If no hole is found, the sensing pin strikes against the coding wheel and nothing is recorded. c. There are only four sets of sensing pins on the coding levers. The fi rst and last coding levers do not have sensing pins attached to them, be cause the coding

19、wheel has no holes above the fi rst and last coding levers. The fi rst set of cod ing levers (farthest from the impulse generator) is not used; only the dot coding lever is used in the last set (closest to the impulse generator). This last dot coding lever is used for automatic character spacing rat

20、her than hole detecting. d. The sensing pin scanning sequence begins with the outside hole on the coding wheel and works inward. There is a hole in the coding wheel for each dot or dash in every character; two holes are never adjacent, because this con dition would allow both a dot and a dash.to be

21、recorded simultaneously. Character P, for exam ple, has holes in the dot row above the fi rst and fourth sensing pins, and holes in the dash row above the second and third sensing pins. e. Assume that the character E to be indexed is in the coding position. The fi rst dot sensing pin will enter the

22、hole in the coding wheel. The fi rst dash sensing pin is blocked by the lack of a hole and it strikes against the coding wheel. As the fi rst dot sensing pin enters the hole, it allows its respective sipning-fl oaded coding lever to pivot, and the dot coding lever bail de presses. This bail is depre

23、ssed by any dot coding lever if its pin enters a hole. Since both the dot switch and the dot bellcrank are directly con nected to the bail through the switch-and-bell crank actuator, the dot switch is closed, and the bellcrank pushes the stroking fi nger out ward to engage the dot universal bar. Sim

24、ultane ously, the impulse generator armature is moved into cocked position by the impulse generator ac tuating cam. /. The sensing pin is now in the hole, the dot switch to the recording head is closed, the stroking fi nger is in the engaging position, and the impulse generator armature is cocked. F

25、ur ther rotation of the operating handle releases the armature sharply, which causes an impulse of current to be delivered to the dot track, and a magnetic impulse is recorded in the dot channel on the tape. Following impulse delivery, the stroking fi nger is pushed downward by a lever that follows

26、the dot stroking cam, and the stroking fi nger engages and depresses the dot spacing universal bar. This movement causes the spacing mechanism to advance the feed ratchet one tooth for the dot space. A one-tooth advance on the feed ratchet rotates the cartridge drive t - M r r gear to cause a two-ba

27、ud, or 0.030-inch tape ad vance. g. Continuing rotation of the operating handle causes the above coding sequence to be repeated on each of the three remaining active dot coding levers; but, since no holes occur in these three remaining positions, no magnetic impulse is recorded and no tape advance o

28、ccurs. h. Operation of the dash coding assembly is the same as the dot coding sequence, except that the dash stroking fi nger engages the dash spacing universal bar and causes the feed ratchet to advance two teeth to cause a four-baud, or 0.060-inch tape advance. i. In the fi nal movement of the ope

29、rating handle, the last (sixth) dot coding lever pivots. The sensing pin is missing from this lever which allows it to pivot completely despite the lack of a hole in the coding wheel. The last (sixth) dash coding lever has no effect because its cam is not recessed. ;. As the last coding lever pivots

30、, the dot coding lever bail is again depressed, which causes both the dot switch to be closed and the TM Hlu-5i83l5-224-35 bellcrank to push the stroking fi nger outward to engage the dot spacing universal bar. Normally, the impulse generator is cocked and released just after the stroking fi nger is

31、 pushed out; but the impulse generator actuating cam has no depres sion at this position, and therefore, no impulse is generated or recorded on the tape. k. As the operating handle approaches its stop, the stroking fi nger is pushed downward and depresses the dot spacing universal bar. Again this mo

32、vement causes the spacing mech anism to advance the feed ratchet one tooth for a dot space, therefore, the fi nal action of the op erating handle creates a blank dot space which is the automatic character space at the end of each character. I. When the word-space button is operated, it depresses the

33、 dash spacing universal bar, and causes the feed ratchet to advance two teeth to cause a four-baud, or 0.060-inch advance. This four-baud advance, added to the three-baud space that follows each character, gives a seven-baud space between words. r 15 TM Tltj3l5u224-3S l CODING WHEEL MORSE CODE HOLE-

34、PATTERNS DOT V. 3 1 DASH TAPE IN CARTRIDGE L R E C O R D I N G L H E A D fl MECHANICAL FUNCTION ELECTRICAL FUNCTION w I 13 TA P E F E E D * CARTRIDGE DRIVE GEAR TM5835-224-45-4 Figure 1-2. CO/B-8 coder, block diagram. Section IV. FUNCTIONING OF CO-3B CODER 1-15. CO-3B Coder Block Diagram For descrip

35、tive purposes, the CO-3B coder mechanism (fi g. 1-S) may be divided (into fi ve basic sections, according to function. A descrip tion of each function is given in paragraphs 1-16 through 1-20. 1-16. Keyboard The keyboard consists of the dot, dash, and space keys. When the dot key is depressed, it en

36、gages and depressed both the spacing universal bar and the impulse generator universal bar, and closes the dot switch to the dot track of the re cording head. When the dash key is depressed, it also engages and depresses both the spacing universal bar and the impulse generator uni versal bar, but cl

37、oses the dash switch to the dash track of the recording head. When the space key is depressed, only the spacing universal bar is depressed. 1-17. Impulse Generator (CO-3B) The impulse generator is the electrical power- plant of the CO-3B coder. It consists of a permanent-magnet structure with a fl a

38、t, spring steel armature surrounded by a coil. The CO-3B coder and the CO/B-8 coder impulse generators are identical. Refer to paragraph 1-10. 1-18. Dot and Dash Switching Assemblies (CO-3B Coder) The negative-current impulse from the generator is switched to either the dot or dash track winding on

39、the dual-track recording head by 3 1-6 TM 11-5835-224-35 r means of two spdt switches that comprise the switching assemblies. These switches are actu ated by their respective dot or dash key. Nor mally, the switches ground the head windings when they are not in use, to prevent stray pickup from bein

40、g recorded. When either switch is en gaged by its respective key, the switch opens the groundpath and connects its respective record ing head track to the (impulse generator in antic ipation of the current impulse. 1-19. Recording Head (CO-3B Coder) Whenever an impulse of current passes through eith

41、er track on the recording head, iron oxide particles embedded in the magnetic tape are magnetically polarized. This magnetic polariza tion creates a magnetic impulse on the tape, which produces the actual recording process. 1-20. Spacing Mechanism (CO-3B Coder) The spacing mechanism is used for prop

42、er tape advance of dots, dashes, and spaces. Information given in paragraph 1-11 is also applicable to the CO-3B coder. r 1-21. Sequence of Functioning (CO3B Coder) a. As the dot key is depressed, the following actions take place: (1) The dot spacing universal bar is de pressed. (2) The dot switch i

43、s closed. (3) The impulse generator universal bar is depressed. b. When the dot key depresses the dot spacing universal bar, the bar engages the spacing mechanism feed pawl and causes it to index one tooth of the feed ratchet in anticipation of ro tating the feed ratchet one tooth when the key is re

44、leased. c. When the dot key is depressed, the dot switch actuator bar engages the dot switch leaf, closes the switch which opens the dot track ground circuit, and connects the dot track to the impulse generator in anticipation of the current impulse. d. When the dot key depresses the impulse generat

45、or universal bar., it strokes the impulse generator armature. An impulse of current is de livered to the dot track of the recording head through the previously closed dot switch and a dot impulse is recorded. e. As the dot key is released, its return (up ward) motion causes the feed pawl to rotate t

46、he feed ratchet one tooth (as previously indexed) for the dot space. This one-tooth advance on the feed ratchet causes a two-baud, or 0.030-inch tape advance. /. When the dot key is depressed, the spacing mechanism is indexed one tooth, the dot switch is closed, and an impulse is recorded. When the

47、key is released, the spacing mechanism advances the tape 0.030 inch, the dot switch is opened, and the dot track is returned to ground. g. Dash key (fi g. 2-12) operation is the same as the dot key operation, except that the dash switch is closed and the spacing mechanism is ad vanced two teeth; the

48、 tape is advanced 0.060 inch for the dash space. h. When the space key is depressed, only the spacing universal bar is depressed, which causes the feed ratchet (fi g. 2-11) to be indexed one tooth. When the space key is released, the spacing mechanism is advanced one tooth and causes the tape to be

49、advanced 0.030 inch for a space. r 1-7 TM 11M5I83I5-224-35 .MECHANICAL FUNCTION ELECTRICAL FUNCTION CA-3B CARTRIDGE DRIVE GEAR 3 * TAPE FEED TM5835-224-45-5 3 Figure IS. CO-SB coder, block diagram. Section V. FUNCTIONING OF CA-3B CARTRIDGE 1-22. CA-3B Cartridge, Block Diagram In operation, the CA-3B cartridge (fi g. 1-4) is attached to the CO-3B coder or CO/B-8 coder for recording; the takeup spool of the CA-3B cartridge is driven clockwise by the drive gear of the operating CO/B-8 or CO-3B coder and causes the tape to advance over the operating CO/B-8 or CO-3B coder recordin