ETL600 1KHW001489-EN ABB Switzerland Ltd
3.3.6. DC-DC converter B4LE
The DC-DC converter type B4LE is used for converting the 48 V DC
into ±12 V DC and +5 V DC voltages which are required by the
modules of the channel rack. These voltages are internal to the
equipment and not available externally. The ±12 V DC lines are
monitored by P4LT for undervoltage and overvoltage. The power
supply can source current for modules of both channel 1 and 2. It may
be noted that B4LE is mounted on the extreme left of P7LC. It is
covered by a dummy plate which is not attached to the B4LE.
The unit includes the following protective functions:
• Inrush current limiter,
• 6.3 A fuse (slow blow) at input,
• Power overload and no load protection,
• Overcurrent and short circuit protection,
• Overtemperature protection,
• Protection against reversal of polarity (with fuse),
• Overvoltage protection on the outputs.
3.3.7. Channel subrack P7LC
The channel subrack P7LC is used to house the optional interface
boards O4LE and G4AI, the DC-DC converter B4LE, the RF converter
P4LT, the optional receive filter P4RX and the optional alarm relay
module R1BC, the latter being mounted onto the backplane in the rear.
All boards except R1BC are plugged form the front side ito the
subrack. Connectors for interface cables are in the rear of the
equipment with the exception of the data connectors of P4LT that are
on the equipment front.
3.3.8. 40 W power amplifier P1LA
The P1LA is mounted on the rear side of the power subrack P7LA.
The RF signal in the power amplifier passes through preamplifiers to
the driver circuits. A combined current/voltage feedback ensures a
minimum of distortion due to non-linearity and a constant output
impedance. The driver circuit provides the low source impedance
necessary for the correct operation of the output amplifier stage. The
signal amplified by the push-pull output stage is combined in the
output transformer, from which it goes to the high power transmitter
filter E5TX.
Structure and Function November 2005 3-29
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