Telex BTR-200 Series manual Receive Board

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RECEIVE BOARD

() CIRCUIT DESCRIPTION

PCB 70714000

This unit is a four channel single conversion receiver consisting of one front end and four I.F. strips. Signals entering the board proceed through 3 tuned circuits, Q30l, and 3 more tuned circuits to the mixer. MX301 is a doubly balanced diode mixer and receives +7 dBm from the oscillator. Q302 is a Colpitts oscillator with the collector tuned to the second harmonic. Y301 operates on the fifth overtone with C319 and L308 acting as mode suppressor. L310 is used to set the oscillator on frequency. From the mixer the signal continues through a broadband filter to line driver Q303. VR309 is used to set the collector current to 20 rnA. Q303 drives the four I.F. strips, beginning with crystal filters FL30l-FL308. The four I.F. strips are the same except for component values. Also, the 10.7 MHz I.F. substitutes a ceramic filter for two tuned circuits. For the remainder of the description the parts in the 10.7 MHz I.F. will be referred to. The I.F. signal is amplified by Q304 and U301A, and limited and detected by U301B. U301B contains a quadrature detector which is tuned by T309. Squelch is of the amplitude type, the D.C. voltage at pin 5 of U301 varying in propOltion to the signal strength. With no signal U302 pin 1is low and the audio outputis squelched. When the received signal causes the voltage at pin 3 of U302 to exceed that of pin 2 of U302, pin 1 goes high and the squelch opens. VR30l sets the threshold at pin 2 and thus the squelch. R320 provides hysteresis. Q305 is used to drive the LED on the front panel. From U301 the audio is amplified by U303A. R389, R328 and C354 set the de-emphasis at 115uS. VR302 is used to com- pensate for variations in detector output level. U303B is a 3 pole ButterwOlth low pass filter with a cutoff frequency of 10KHz.

PCB 750309

This unit is a four channel dual conversion receiver consisting of one front end and four I.F. strips. Signals entering the board proceed through 3 tuned circuits, Q301, and three more tuned circuits to the mixer. HY301 is a doubly balanced diode mixer and receives +7 dBm from the oscillator. Q302 is a Colpitts oscillator with the collector tuned to the second harmonic on version 1 boards and the third harmonic on version 2. Y301 operates on the fifth overtone with C311 and L308 acting as mode sup- pressor. L307 is used to set the oscillator on fre- quency. From the mixer the signal continues through Q303 to filtet drivers Q320, Q370, Q420 and Q470. On version 1 boards the signal is resis- tively coupled to the filters. On version 2 boards it is inductively coupled. The four I.F. strips are the same except for component values. For the remainder of the description the parts in the 10.7 MHz I.F. will be referred to. U320A mixes the incoming signal with a 10.245 MHz oscillator to produce the second I.F. of 455 KHz. (The other three oscillators operate at 455 KHz above their n~spective input frequencies). U320B contains a limiter and quadrature detector, which is tuned by L322. U320C functions as a 94 KHz bandpass filter for operating the squelch. With. no signal a large amount of noise is present at U320 pin 13 and a portion of this is rectified by Q321. If the emitter rises above .7V U320D clamps pin 16 to ground, muting the audio, and drives pin 15 low, extin- guishing the LED on the front panel via Q322. When a signal is received, the noise at U320 pin 13 drops and lowers the voltage at the emitter of Q321, releasing the audio clamp and lighting the front panel LED. Since the LED current flows through R33l, the voltage drop acts on Q32l and provides hysteresis. VR321 adjusts not only the noise amplitude delivered to Q321 but also the D.C. bias, and is used to set the squelch at 1 microvolt. From U320 the audio is buffered and filtered by U321. R328, C335, and VR320 set the de-emphasis at l15uS. U321Ais a three pole Butterworth low pass filter with a cutoff frequency of 10 KHz.

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Contents EnW ~iDD ~~~Table of Contents · Transmit, Receive & Audio Circuit Boards DescriptionChapter Controls and Connections Front Panel-BTR200 27160-8-00I-AMIC on PUSIH-lO-TALKI Rear Panel BTR-200 27160-B-002-ASpeaker / Local Monitor 8 n MIN Rear Panel Refer to Figure Location of Rev Level for Versions 1 Location of Rev Level for Versions 3 thruReceive Board Transmit Board Places Mechanical PartsExploded View· BTR-200 TRANSMIT, Receive & Audio CIRCUIT,BOARDS Transmit Board Q50l Q502 Q503 Device 1====-r===r===r====jPI=N=N=U=rM=B=EFR==~===r==~==l1U501 +~04 ~@C501Transmit Board Component Layout Foil Side Transmit Board Component Layout Component SideQ503~502 Schematic Diagram Transmit Board Version 100P~PCB Transmit Assembly Receive Board Receive Board Receive Board Page Page Q301 Q309, Q311Q302 Q303 Q304 Q311 U304 U306 U309Voltage Tables· Receive Board Voltage Tables Receiv~ Board U303 U305 U307 U310 550 234876 U302 123Lp~lr FL30~368@ ~ ~@R33~@R334@ a ~050Schematic Diagram Receive Board Version 1 PCB Assembly ~~VC303I6i?7 Receive Board Componen~Layout Foil SideL4~ Receive Board Component Layout Component Side VersionCJl~VOB Frequency Dependent Components TablePCB Receive Assembly PCB Receive Assembly PCB Receive Assembly 878522M VC301-VC308 GAASFET, NE PCB Receive Assembly Receive Expanders Microphone AmplifierAuxiliary Input Amplifier Intercom DriverPower Supply Intercom InputHeadset and Speaker Amplifiers Transmit Mixer and Filter29/3-30 Blank Block Diagram Versions 1 ToI +0 0+ ~OEg+0 Rl~63 jRl02Ov· \.AJAudio Board Component Layout Foil Side Versions 1 UrI ~R17JSchematic Diagram Audio Board Version R1,~HEAO~.~22C113Jo ~C-\1ilBlI.0U~r.VY..,R137LI~-.=Joqa ~.C·@5It Details of Board Differences Between Versions 1DCD R182 C142 ~S~!~ ~lll~0113 CJC~5 +~87Audio Board Component Layout Foil Side Versions 3, 4,~I~ ~4~ ~4S C2~~~R230-------L.jN,-.L!~2.-.L-.-H~B~~9 R21~1Daoa CI6~~ ~EM32~Ms~ ~ R224 E I fJJ~F~IR~~~~199r~ C117H!f-V1\M,pI~£.jl,ltI1Ir-1N+--J ~1~1~2 +lQJl~iPCB Audio Assembly, 878520 Versions 1 thru PCB Audio Assembly 878520 Versions 1 thru Rln·2 Rln36Tioi Display Board Component Layout Foil Side Display Board Component Layout Component ViewTELEX@

BTR-200 Series specifications

The Telex BTR-200 Series is a well-regarded solution in the realm of wireless intercom systems, widely utilized in broadcast, film, and live event production settings. Renowned for its reliability, user-friendly interface, and robust performance, the BTR-200 Series has become a staple for professionals seeking efficient communication solutions.

One of the standout features of the BTR-200 Series is its frequency agility. The system operates in the UHF band, allowing users to switch frequencies to avoid interference from other wireless devices. This adaptability is crucial in environments where multiple wireless systems operate simultaneously. Users can easily reprogram frequencies to ensure clear and uninterrupted communication among team members.

Another key characteristic of the BTR-200 Series is its impressive range. The systems can provide coverage up to 1,000 feet in line-of-sight applications, making it suitable for large venues. This extensive range ensures that communication remains intact even in expansive settings, such as concert halls or outdoor arenas. Additionally, the enhanced RF performance ensures minimal dropouts, contributing to seamless communication.

The BTR-200 Series also distinguishes itself with its digital circuitry, which enhances audio clarity and reduces noise. This reliance on advanced technology results in crisp communication that is essential for coordinating complex productions. The system also features a low-latency design, which is particularly valuable in live performance settings where timing is crucial.

In terms of user interface, the BTR-200 Series is engineered with simplicity in mind. The beltpack units and base station feature intuitive controls that enable quick adjustments, making them easy to operate even under the pressures of a production environment. Each beltpack supports individual volume control, allowing users to customize their audio experience according to their preference.

Moreover, the BTR-200 Series is built for durability and long-lasting operation. The robust construction of its components ensures reliability, even in challenging environments. Rechargeable batteries offer extended operating time while reducing the need for constant replacements.

In summary, the Telex BTR-200 Series stands out for its frequency agility, extensive range, digital audio clarity, user-friendly interface, and durable build quality. These features combined make it an ideal choice for professionals in the broadcasting and live event production industries, promoting seamless and efficient communication essential for successful operations. The BTR-200 Series remains a trusted solution, proving its worth time and again in various high-pressure scenarios.
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