Telex 38109-977 manual Ccu

Bridging

BW

Byte

Bridging impedance means an impedance that when paralleled with a nominal impedance will have an non-significant effect on a circuit. For example: for a nominal impedance of 600 ohms, a parallel impedance of 3,000 ohms (5 times) would make the net impedance 500 ohms, 17 percent less than 600 ohms or 1.6 dB. A parallel impedance of 6000 ohms (10 times) would cause about a 9 percent change or about a 0.82 dB difference. A parallel impedance of 12,000 ohms (20 times) results in about a 3 percent change or 0.26 dB. In present day audio systems, line level and power amplifiers have input impedances specified at 600 ohms or 15,000 ohms. Microphone preamplifiers are usually ten times the expected source impedances. For example: for 150 ohm microphones the input impedance is 1,500 ohms or greater. Earlier RTS™ Systems intercoms also had this microphone input value, but a compromise value of 470 ohms was necessary because of the crosstalk in headset cords. However, RTS™ Systems professional audio equipment generally adheres to current audio standards.

Bandwidth.

Eight binary digits or bits.

C

Call light

Capacitance

Capacitive

Reactance

Capacitor

Cardioid Pick- up Pattern

CCU

Channels and Buses

A feature in intercoms that is used for two different purposes: 1) To get a user to put his headset back on (blinking call light). This method is the standard way for RTS™ Systems equipment. 2) To generate a cue (steady call light). The usage in this case is often as follows: light on means standby, light off after light on means execute. This method is used by other manufacturers and IS optional with RTS™ Systems equipment. In some user stations, the call light feature is standard (BP325, MCE325), in other stations, it is an option.

The ability to store electrical charge between two conductors. Measured in farads (Named after Michael Faraday). A capacitance value of one farad can store one coulomb of charge at one volt. One farad permits one ampere of current when the voltage changes at the rate of one volt per second. Typical sizes are measured in: millifarad one-thousandth of a farad microfarad one- millionth of a farad nanofarad one-thousandth of a millionth of a farad picofarad one-millionth of a millionth of a farad.

The opposition to alternating current through a capacitor. Capacitive reactance, Xc is measured in ohms and is equal to: 1 / [2 * π * frequency * capacitance].

Two conducting surfaces separated by a dielectric. The dielectric could be a material, air, or a vacuum. The capacitance of the capacitor is a function of the area of the surfaces, dielectric, and spacing between the conducting surfaces.

The pick-up pattern of a directional microphone is frequently of cardioid (heart) shape. The maximum cancellation (minimum pick-up) occurs at an angle of 180°. The sound power concentration is approximately three times.

Camera Control Unit. Usually located in an equipment room (studio) or a bay in a mobile truck (mobile). The CCU is connected to the camera “Camera Head” via a cable. The cable is either wire “multicore,” triaxial cable “triax,” or coaxial cable “coax.”

Channels and Buses are pathways for signals to travel. There are more than one channel or bus to allow for multiple conversations or information flows to occur simultaneously. Multiple buses separate signals using space and the process is sometimes called space multiplexing.

Analog Channels and Buses In the discussions here, analog Channels or buses carry signals representing audio. There is an exception, the call light signal is superimposed over the signals representing audio. This signal is not heard by humans because of its 20.0 kilohertz frequency. In this case the voice audio and the call light signal are multiplexed using frequency separation. The words “channels” and “buses” are often used interchangeably. In a twelve channel or bus system, it is possible for a user station to be tied to say system bus 5 and system bus 3 when the user station channel selector switch reads 1 and 2 respectively. For purposes of distinction, discussions that talk about system channels or buses and user station channels, the word bus will refer to system buses and the word channel will refer to user station channels.

132 H a n d b o o k o f I n t e r c o m S y s t e m s E n g i n e e r i n g