20.10.1 Noise contributions

Noise contributions are defined on a per channel basis in pWOp.

Table 20.9 Design targets for noise contributions from open wire systems with 2500km circuit length

Table 20.10 Design targets for noise contributions from metric pair cable systems, coaxial cable and radio systems with 2500 km circuit length

Recommended design targets are included in Tables 20.9 and 20.10. The line equipment noise figure in Table 20.10 corresponds to 3pWOp per km. For wideband services, such as TV transmission, the equivalent requirement is more onerous at 1.5pWOp mean noise contribution per km.

20.10.2 Line sections

The following applies:

1. The coaxial cable hypothetical systems are constructed from homogeneous line sections of 280km.

2. The change of gain of a regulated 280km homogeneous line section due to seasonal changes in the cable loss, time etc. will not be greater than 1 dB.

3. Unwanted modulation products from low frequencies (50Hz etc.) will not be greater than 48dBmO for a 280km homo­geneous line section. A similar requirement is placed on the multiplex equipment.

1 Learn the words & word combinations:

White noise	Белый шум
NPR	Коэффициент мощности шума
Robustness	Устойчивость
Loading factor	Коэффициент загрузки
Binominal distribution	Биполярное распределение
Channel capacity	пропускная способность число каналов системы
Gain	Коэффициент усиления
Degradation factor	Коэффициент снижения производительности
Companding	Компандирование
Compander	Компандер
Compression ratio	Коэффициент уплотнения
Attenuation	Затухание, ослабление, коэффициент затухания
Circuit noise	Шум линии связи, шум тока передачи
Impairment	Ухудшение, повреждение
Attack time	Время нарастания (сигнала)
Decay time	Время затухания сигнала
Through connection	Транзитное соединение

2 Read & translate the text (orally) 20.8 -20.10:

3 Find Russian equivalents:

White noise measurement	rapid field evaluation
bench evaluation of individual circuits	a flat frequency spectrum of noise the noise power ratio
the channel loading factor	the system overload requirements

4 Find English equivalents:

как … так и	позволяет
общая мощность	переключатель
непрерывный	несколько
изменять	различные условия
преобладать