8571—Brief description
NGT Transceiver System Technical Service Manual
333
General information
Application of a 300 Hz control tone from any point removes all audio from the system
in preparation for data signalling. Data is used to communicate to and from all
microprocessors within the network and includes commands such as select Transmit
mode (PTT), channel change, system status and so on.
In the absence of the control tone, the system provides an audio path from the
transmitter/receiver through the 8571, via the land line (2-wire) or VHF/UHF radio link
(4-wire), to one or more master control points.
When sending data, the control tone is present for the duration of the signalling, and on
completion of the data transmission, reverts to the Receive mode. Data is transmitted in
simplex mode at 550 baud using FSK.
The control tone is notched out of all external audio paths.
Receive audio path
In Receive mode, audio from the transceiver is applied to the Rx slave 8571 via an
interface cable. The audio passes through a 300 Hz notch filter IC3 and IC4 to remove
any 300 Hz that may be present in the receive audio that could possibly corrupt the
performance of the system. The signal output from the filter is connected to a gain-
controlled amplifier/compressor IC7 to maintain a constant audio output level.
At the output of IC7, the audio is fed via the signalling modem IC6 to the line driver
IC102 and is then connected to either a 2-wire private line via the hybrid and first
isolating transformer, or to a second isolating transformer for the 4-wire system.
At the other end of the 2-wire or 4-wire link, the received audio is applied to the 8571 via
the appropriate isolation transformer to a hybrid and then to the first amplifier IC101.
From the output of this amplifier, the 300 Hz control tone is fed via a 300 Hz BPF IC106
(to remove the receive audio) to a threshold detector IC104a/IC107. The receive audio is
applied to a DC gain-controlled amplifier IC103a, then to a DC-controlled equaliser
IC103b/IC104b. From here it passes via a 3 kHz LPF IC105a through a switch, selected
to a 300 Hz notch filter, to remove the 300 Hz control tone, and finally via an interface
cable to the split-site interface controller receive audio path.
NOTE
The information in this section should be read in conjunction with the
block diagram
.
Summary of Contents for NGT 2010 RF
Page 87: ...03 01032 Issue 2 ...
Page 88: ...03 01032 Issue 4 ...
Page 97: ...03 01126 ...
Page 98: ...03 01190 ...
Page 428: ...04 03223 ...
Page 429: ...04 03562 CODAN ...
Page 430: ...04 03437 ...
Page 431: ...04 03533 ...
Page 432: ...08 05513 ...
Page 433: ...08 05514 sheet 1 ...
Page 434: ...08 05514 sheet 2 ...
Page 435: ...08 05628 sheet 1 ...
Page 436: ...08 05628 sheet 2 ...
Page 437: ...08 05628 sheet 3 ...
Page 438: ...08 05628 sheet 4 ...
Page 439: ...04 03125 ...
Page 440: ...08 05300 ...
Page 441: ...08 05522 ...
Page 442: ...08 05523 ...
Page 443: ...08 05524 ...
Page 444: ...04 03201 ...
Page 445: ...08 05470 ...
Page 446: ...04 03423 ...
Page 447: ...08 05986 sheet 1 ...
Page 448: ...08 05986 sheet 2 ...
Page 449: ...04 03133 ...
Page 450: ...08 05317 ...
Page 451: ...04 03109 ...
Page 452: ...08 05266 ...
Page 453: ...04 03108 sheet 1 ...
Page 454: ...04 03108 sheet 2 ...
Page 455: ...08 05265 ...
Page 456: ...04 03106 sheet 1 ...
Page 457: ...04 03106 sheet 2 ...
Page 458: ...04 03106 sheet 3 ...
Page 459: ...08 05261 sheet 1 ...
Page 460: ...08 05261 sheet 2 ...
Page 461: ...04 03095 ...
Page 462: ...08 05235 ...
Page 463: ...04 03378 sheet 1 ...
Page 464: ...04 03378 sheet 2 ...
Page 465: ...04 03378 sheet 3 ...
Page 466: ...04 03378 sheet 1 ...
Page 467: ...04 03378 sheet 2 ...
Page 468: ...04 03378 sheet 3 ...
Page 469: ...08 05889 sheet 1 ...
Page 470: ...08 05889 sheet 2 ...
Page 471: ...08 05889 sheet 1 ...
Page 472: ...08 05889 sheet 2 ...
Page 473: ...04 03410 ...
Page 474: ...04 03414 ...
Page 475: ...08 05963 ...
Page 476: ...08 05962 ...
Page 477: ...08 05973 ...
Page 478: ...04 03169 ...
Page 479: ...08 05415 ...
Page 480: ...08 05416 ...
Page 481: ...08 05511 sheet 1 ...
Page 482: ...08 05511 sheet 2 ...
Page 483: ...04 03369 ...
Page 484: ...08 05869 sheet 1 ...
Page 485: ...08 05869 sheet 2 ...
Page 486: ...08 05869 sheet 3 ...
Page 487: ...08 05910 sheet 1 ...
Page 488: ...08 05910 sheet 2 ...
Page 489: ...04 03542 ...
Page 490: ...08 06461 sheet 1 ...
Page 491: ...08 06461 sheet 2 ...
Page 492: ...08 06461 sheet 3 ...
Page 493: ...08 05910 sheet 1 ...
Page 494: ...08 05910 sheet 2 ...
Page 495: ...04 03425 ...
Page 496: ...08 05988 sheet 1 ...
Page 497: ...08 05988 sheet 2 ...
Page 498: ...04 03424 sheet 1 ...
Page 499: ...04 03424 sheet 2 ...
Page 500: ...08 05987 ...
Page 501: ...04 03499 sheet 1 ...
Page 502: ...04 03499 sheet 2 ...
Page 503: ...08 06261 sheet 1 ...
Page 504: ...08 06261 sheet 2 ...
Page 505: ...04 03498 sheet 1 ...
Page 506: ...04 03498 sheet 2 ...
Page 507: ...08 06260 ...
Page 508: ...04 03379 ...
Page 509: ...08 05890 ...
Page 510: ...15 10506 001 ...
Page 511: ...15 10514 001 ...
Page 512: ...04 03110 ...
Page 513: ...08 05267 ...
Page 514: ...04 03514 ...
Page 515: ...08 06320 ...
Page 516: ...04 03272 ...
Page 533: ...03 01138 ...
Page 534: ...03 01139 ...
Page 604: ...04 03422 ...
Page 605: ...08 05985 ...
Page 606: ...04 03419 ...
Page 607: ...08 05997 ...
Page 608: ...04 03420 ...
Page 609: ...08 05999 ...
Page 610: ...04 03416 ...
Page 611: ...08 05977 sheet 1 ...
Page 612: ...04 03428 ...
Page 613: ...08 05998 ...
Page 614: ...04 03429 ...
Page 615: ...08 06000 ...
Page 616: ...04 03415 ...
Page 617: ...08 05976 sheet 1 ...
Page 618: ...08 05976 sheet 2 ...
Page 619: ...04 03418 sheet 1 ...
Page 620: ...04 03418 sheet 2 ...
Page 621: ...08 05979 sheet 1 ...
Page 622: ...08 05979 sheet 2 ...
Page 623: ...04 03417 ...
Page 624: ...08 05978 sheet 1 ...
Page 625: ...08 05978 sheet 2 ...
Page 626: ...08 05978 sheet 3 ...
Page 627: ...04 03421 ...
Page 628: ...08 05984 ...
Page 629: ...04 03453 ...
Page 630: ...08 06067 sheet 1 ...
Page 631: ...08 06067 sheet 2 ...
Page 632: ...08 06102 sheet 1 ...
Page 633: ...08 06102 sheet 2 ...
Page 634: ...04 03377 ...
Page 635: ...08 05926 sheet 1 ...
Page 636: ...08 05926 sheet 2 ...
Page 637: ...04 03407 ...
Page 638: ...08 05927 sheet 1 ...
Page 639: ...08 05927 sheet 2 ...
Page 654: ...03 01079 ...
Page 700: ...04 03363 sheet 1 ...
Page 701: ...04 03363 sheet 2 ...
Page 702: ...08 05854 sheet 1 ...
Page 703: ...08 05854 sheet 2 ...
Page 704: ...08 05854 sheet 3 ...
Page 705: ...04 03364 ...
Page 706: ...08 05855 ...
Page 707: ...04 03370 ...
Page 708: ...08 05870 ...
Page 721: ...03 01080 ...
Page 749: ...04 03366 sheet 1 ...
Page 750: ...04 03366 sheet 2 ...
Page 751: ...08 05860 sheet 1 ...
Page 752: ...08 05860 sheet 2 ...
Page 753: ...04 03367 ...
Page 754: ...08 05861 ...
Page 771: ...03 01108 ...
Page 826: ...08 05994 sheet 1 ...
Page 827: ...08 05994 sheet 2 ...
Page 828: ...04 02541 ...
Page 829: ...08 03905 ...
Page 830: ...04 02690 ...
Page 831: ...08 03993 ...
Page 832: ...04 02691 ...
Page 833: ...08 05995 ...
Page 834: ...04 02852 ...
Page 835: ...08 04644 ...
Page 836: ...04 02487 ...
Page 837: ...08 03817 ...
Page 838: ...08 03995 ...