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Installation instructions for remotely fed devices (VOS 138/RA, VOS 139/RA)
In accordance with EN 60728-11, remote feed voltages up to a maximum of 65 V AC are permissible. Voltages above 50 V AC are
already considered dangerous to touch. Therefore they may not be accessible to laymen and only accessible to persons with electrical
instruction by using tools.
If the shield of the current-carrying coaxial cable (outer conductor) is broken at any point the remote power feed may appear at the
metal housing of the device (touch hazard!). Therefore the outer conductor connection of the remote feed cable may never be separated
before its inner conductor connection (for safety, always switch off the remote feed). Great care must be taken in establishing a
safe outer conductor contact (be sure to follow the manufacturer's instructions!).
Protective measures
Potential equipotential by local earthing point
An additional connection to earth potential must be made at the earthing point of the device by way of a copper conductor with at least
4 mm
2
cross-section. This connection can be made to an existing earthing rail or a local earth for example.
If this cannot be achieved, one of the following protective measures may be taken:
a) Potential equalisation by minimum cross section of the coaxial cable
It must be ensured at all times that the remote feed coaxial cable has an outer conductor cross-section of at least 4 mm
2
along its entire length (from the feed-in point) (Note: braided cables do not generally have this cross section).
or
b) Potential equalisation by several connected cables
It must be ensured that at least one other coaxial cable is permanently connected to earth potential on its shield along
its entire length.
or
c) Potential equalisation in manual range
Potential equalisation must be carried out in the manual range of the device, i.e. within 2.50 m. For this, all live parts
within this range must be connected to the device by way of at least a 4 mm
2
copper conductor.
or
d) Protection against contact by installation in closed operating rooms
Remotely powered devices must be operated in locked operating rooms. A relevant warning (such as a lightning
symbol and the phrase “Shock hazard in case of fault”) must be af
fi
xed indicating that in the event of a fault supply
voltage potential may be connected to the unit chassis. Cables leading directly to the subscriber must in this
case be equipped with electrical isolation on the outer conductor.
or
e) Maximum remote feed voltage limited to 50 V AC
The remote feed voltage in the system may not exceed a max. 50 V AC.
When supplying multiple VOS 139/RA (via direct connection), it is essential to ensure the correct polarity!
Risk of short circuits!
Optional accessories
■
De-emphasis equaliser:
ERD 810, ERD 813, ERZ 940
■
Pre-emphasis equaliser:
ERZ 630, ERS 800
■
Cable
fi
ttings:
EMP 26, EMP 28, EMP 34,
EMP 35
■
Remote feed transformer:
TVF 20
Test sockets
Test socket on the ampli
fi
er input
5-1006 MHz two-way (switchable)
dB
-20
Test socket on the ampli
fi
er output
5-1006 MHz with directional coupler
dB
-20
Test signals for the return path can be injected at the output test
socket.
