Read the text and be ready to answer the questions after the text

Amplifiers are essential units of terminal and intermediate apparatuses in multichannel systems. Amplifiers used in radio communication are divided into individual, generic and single-component signal amplifiers.

Individual amplifiers are designed to intensify signals in single channels. In modern multichannel systems which are built, as a rule on, the basis of generic principle, such amplifiers are used only in individual part of a terminal apparatus, amplifiers being installed after demodulator (a signal converter), therefore, they become amplifiers of sonic frequency. In multichannel systems created on the base of individual principle, individual amplifiers are used both in terminal and in intermediate apparatuses as means of intensification of high frequency current. Duplex amplifiers are individual too.

Generic amplifiers are used to intensify signals in channel banks. They are used both in batches of terminal apparatuses and in intermediate apparatuses of multichannel systems built on the base of batch principle. Both batch and individual amplifiers are used to intensify multichannel signals; hence, they should be aperiodic.

In addition to individual and batch amplifiers, in apparatuses of multichannel systems there are amplifiers which intensify the carrier current and currents of different controlling signals – pilot frequencies, telecontrol signals, and selection and calling signals. These signals are mostly fixed-frequency (sine) signals. Resonance amplifiers are used to intensify them.

Signal amplification can be provided either in frequency without its conversion or with conversion of frequency. Receiver intensifying radio frequency is called straight amplifier: receiver converting frequency in radiotrackt is called superheterodyne. Frequency amplifiers provide frequency intensification and its subsequent noise filtering.

Main electric properties of multichannel systems amplifiers are: gain factor or intensifying possibility of an amplifier and its frequency relation; input and output resistance of an amplifier; output power of an amplifier; gain compression appearing in amplifier; amplifier noises.