Fixed Beam A fixed beam configuration has both ends of the beam rigidly attached to the supports. Cable ladder systems and cable tray systems shall be manufactured in accordance with BS EN 61537, channel support. OBO BETTERMANN has offered prod-ucts and solutions for electrical instal-lation for over 100 years. With our many years of experience, we are one of the leading manufacturers in this field. It is available with a ventilated or solid bottom. Of course. Cable Tray Selection - Strength Deflection Deflection in a cable tray system is primarily an aesthetic consideration.