1. Types of interference sources

● The source of interference from the construction of the computer room

(1) High -frequency interference generated by the distribution network and power distribution box.

(2) Harmony interference caused by high -power motor electrical sparks.

(3) Interference caused by fluorescence lamps and electronic ballasts.

(4) Interference generated by high -frequency switching power supply.

(5) The interference generated by the ringing current of the phone.

(6) Periodic pulse interference generated by information processing equipment.

If the computer room comprehensive wiring system cannot keep a safe distance from these interference sources, the shielding system can be used to reduce or eliminate the interference of the comprehensive wiring system.

● The source of interference from the outside of the computer room building

The sources of interference from the outside of the computer room are:

Radar, radio launch equipment, mobile telephone base stations, high -voltage wires, electrified railways, interference signals in the lighting area environment, etc.

Obviously, the external interference sources of intelligent buildings have high electric field strength. When one of the above interference sources outside the comprehensive wiring system of the computer room, the shielding system should also be used.

● The source of interference from the environment around the comprehensive wiring system

The noise level of the interference signal strong or integrated wiring system around the comprehensive wiring system should also be protected by the shielding system when the noise level of the comprehensive wiring system exceeds the following regulations.

(1) When the computer local area network, when the frequency of interference signals introduced is L0KHz ~ 600MHz, the field strength is 1V/m; the frequency of 600MHz ～ 2.8GHz interference signals, and its field strength is 5V/m.

(2) When the introduction of the introduction line with a signal DC or AC, the introduction frequency of 15-80MHz is 3V/m (amplifier 80%, 1kHz) through the interference signal with a frequency of 15-80MHz.

(3) When a terminal device with analog/digital terminal interface provides telephone services, the bandwidth sum of the noise level exceeding 40dB should be less than 200MHz.

(4) Background noise should be at least 12dB than the benchmark level.