Handbook

Axell Wireless Limited
Technical Literature
WMATA CRCS Redundant Antenna System
General Overview
Document Number 60-228701HBK Issue No. 3 Date 28/05/2010 Page 6 of 114
2. Safety Considerations
2.1. Earthing of Equipment
Equipment supplied from the mains must be connected to grounded outlets and earthed in
conformity with appropriate local, national and international electricity supply and safety
regulations.
2.2. Electric Shock Hazard
The risk of electrical shocks due to faulty mains driven power supplies While potentially ever
present in any electrical equipment, would be minimized by adherence to good installation
practice and thorough testing at the following stages:
a) Original assembly.
b) Commissioning.
c) Regular intervals, thereafter.
All test equipment must be in good working order prior to its use. High current power supplies can be
dangerous because of the possibility of substantial arcing. Always switch off during disconnection and
reconnection.
2.3. RF Radiation Hazard
RF radiation, (especially at UHF frequencies) arising from transmitter outputs connected to
AWL’s equipment, must be considered a safety hazard.
This condition might only occur in the event of cable disconnection, or because a ‘spare’
output has been left un-terminated. Either of these conditions would impair the system’s
efficiency. No investigation should be carried out until all RF power sources have been
removed. This would always be a wise precaution, despite the severe mismatch between the impedance of
an N type connector at 50, and that of free space at 377, which would severely compromise the efficient
radiation of RF power. Radio frequency burns could also be a hazard, if any RF power carrying components
were to be carelessly touched!
Antenna positions should be chosen to comply with requirements (both local & statutory) regarding
exposure of personnel to RF radiation. When connected to an antenna, the unit is capable of producing RF
field strengths, which may exceed guideline safe values especially if used with antennas having appreciable
gain. In this regard the use of directional antennas with backscreens and a strict site rule that personnel
must remain behind the screen while the RF power is on, is strongly recommended.
Where the equipment is used near power lines or in association with temporary masts not having lightning
protection, the use of a safety earth connected to the case-earthing bolt is strongly advised.
2.4. Lifting and other Health and Safety Recommendations
Certain items of AWL equipment are heavy and care should be taken when lifting them by
hand. Ensure that a suitable number of personnel, appropriate lifting apparatus and
appropriate personal protective equipment is used especially when installing Equipment
above ground e.g. on a mast or pole and manual handling precautions relevant to items of
the weight of the equipment being worked on must be observed at all times when handling,
installing or dismounting this equipment.