Environmental Considerations of Digital Telephone Switching Systems


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Environmental Considerations of Digital Telephone Switching Systems

5.14.1 Electromagnetic Fields and Electrical Conditions
The digital switching equipment shall be able to withstand electromagnetic fields of the following magnitudes:
a) One (1) volt/meter for frequencies equal or below 1 GHz.
b) Ten (10) volts/meter for frequencies above 1 GHz.
The equipment shall withstand a magnetic field of 10-4 ampere turns per meter at frequencies under 1 KHz. In addition, the equipment supplied shall operate in buildings in which microwave equipment is installed. Refer to SAES-T-903 and SAES-T-887.
The proposed CO digital exchanges shall not be particularly sensitive to static electricity and should comply with the international recommendation for Radio-electronic disturbances.
The equipment shall comply with the following technical requirements of the regulatory standards:
a) FCC: Federal Communications Commission (U.S.A.) Part 15, Radio Frequency Devices – Subparts B and D.
b) DOC: Department Of Communications (Canada) CSA C108.8 (Canadian Standards Association).

Commentary Notes:
 Electro-Magnetic Interference (EMI): EMI is the impairment of a wanted electromagnetic signal by an electromagnetic disturbance.
 Electro-Magnetic Compatibility (EMC): EMC is the ability of a device, equipment, or a system to function satisfactory in its electromagnetic environment without causing or suffering unacceptable electromagnetic disturbance.
 Measuring EMC (Radiated emissions): Radiated emissions are determined by measuring the field strength of the outgoing radiation at a specific distance from the equipment. The unit of measure is microvolts/meter (decibels above one microvolt/meter).
5.14.2 Resistance to Light and Heat
The equipment shall not emit harmful substances when exposed to light and heat, nor shall vital parts be damaged or discolored when exposed to light.
5.14.3 Dust Protection
Equipment and maintenance requirements with respect to air purity and presence of dust particles shall be specified.
To facilitate control of dust, the manufacturer/contractor shall verify, prior to equipment’s installation, that the switching/apparatus rooms are pressurized.
5.14.4 Seismic Requirements and Resistance to Vibrations
Protection must be provided for floor-mounted apparatus to prevent lateral shifting in the event of an earthquake. All power cables, bus bars and other ceiling-supporting runs must be adequately braced for earthquakes.
Manufacturers shall describe how vibrations from machines, vehicle traffic and equipment located near the exchange may affect the operation of the equipment.
5.14.5 Atmospheric Pressure
The exchange operation shall be maintained at atmospheric pressures between 0.795 to 1.05 bars under all operating conditions. When being transported, the system can be subject to pressures between 0.660 and 1.05 bars.

5.14.6 Heating, Ventilation and Air Conditioning (HVAC)
a) Climatic conditions – storage
The components of digital switching equipment shall not be damaged when stored within the following environmental ranges:
1. Temperature: 0°C (32°F) to 70°C (158°F)
2. Relative Humidity: 10 to 95%
b) Climatic conditions – operation
All digital switching equipment shall be capable of operating within the following environment limits without loss of performance.
1. Nominal Operating temperature
 During summertime: 27°C (80.6°F)
 During wintertime: 20°C (68°F)
2. Long-term temperature range
 Year-round: 4°C (39.2°F) to 38°C (100.4°F)
These conditions may be exceeded during transportation. The supplied equipment must be packaged to withstand such conditions without damage.
c) For HVAC system’s specifications, refer to the various applicable documents, and to the following Saudi Aramco standards:
SAES-K-003 Air Condition System for Communications Buildings
SAES-K-100 Saudi Aramco Mechanical (HVAC) Code
5.14.7 Rack and Emergency Lighting
a) Rack Lighting
Suitable rack lighting equipment, if not installed, shall be provided to illuminate the whole apparatus. The power for rack lighting shall be taken from the AC main supply.
b) Emergency Lighting
Emergency lighting from the main exchange battery shall be provided for in the exchange room and all other equipment rooms. A system for automatically switching to emergency lighting in case of mains failure shall be provided by the manufacturer/contractor.
c) For rack and emergency lighting specifications, refer to the various applicable documents, and to the following Underwriters Laboratories Inc. (UL):
UL 924 Emergency Lighting and Power Equipment
5.14.8 Fire Alarm and Fire Detection/Protection Systems
All new digital exchange equipment will be installed in communications buildings with fire alarm, and fire detection/protection system(s) already in place.
For fire alarm and fire detection/protection system’s specifications, refer to the various applicable documents, and to the following National Fire Protection Association codes and standards (NFPA):
NFPA 12A Halon 1301 Fire Extinguishing Systems
NFPA 72E Standard on Automatic Fire Detectors

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