Intercom Input

Since U 107A is a current source, signals arriving from an external intercom appear unloaded at pin 1 and are coupled via C126 and R154 to U106. To prevent intercom output signals from appearing at the output of U106, these signals are nulled by the branch containing C124, VRlOl and R152. U 106A and U 109 form a peak limiting am plifier similiar to that described for the microphone amplifier above, except that CA10l is used instead of a JFET to control the gain. The reason for this is that the higher level signals being handled by U 106A would cause high distortion if a JFET were used. CA10l is merely an LDR (light dependent resistor) together with an LED in the same package. More current through the LED reduces the value of resistance.

Headset and Speaker Amplifiers

U 111 and Ul19B (U107B in versions 1 and 2) drive the headset while U108 drives the external speaker jack. On versions 1 and 2 this signal was derived by mixing the microphone signal with the intercom output, via R175 and R177. On later versions the intercom output alone is used, being first amplified by U119A. S112B maintains the headset/speaker level constant when switching intercom output levels.

Transmit Mixer and Filter

U 106B mixes the intercom input, auxiliary input, microphone and receive board signals together to modulate the transmitter. VR102 is used to set the level going into the transmit compressor for proper tracking. On versions 3 and later, U118 acts as a four pole Chebyshev low pass filter with a cutoff frequency of 5 KHz. This is to prevent transmis- sion of the 20 KHz tone which Telex intercoms use as the call signal.

Auxiliary Output

UllOA mixes together intercom input, microphone, and receive board signals. U11 OB inverts the resultant to provide a balanced output.

Remote Transmit Circuit

When the transmit switch on the rear panel is in the remote position, the transmitter will only operate when at least one receive squelch is open. On versions 1 through 4 this is done with Ul15 which turns on Q109. Versions 3 and 4 have a circuit board error, however, which prevents this option from working. To correct this move the inputs of Ul15 to the left side (on the schematic) of R195, R198, R20l, and R204. The version 3 and 4 schematics show these inputs as they are un- modified, that is, connected to the right side of the resistors. On versions 5 and above, U 115 is replaced with Ql12, Ql13, Ql14 and Ql15 and no modifications are necessary.

Power Supply

Q 108 and U114 form a 10 volt regulated power supply. On versions 1 and 2, ZD101 is used as the 5 volt reference while on later versions this comes from U 117. U 112 and U 113 are also supplied by U1l7.

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Telex BTR-200 Series manual Intercom Input, Headset and Speaker Amplifiers, Transmit Mixer and Filter, Auxiliary Output
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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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