Lectrosonics UDR200b - Manual (Page 8)

REAR PANEL CONTROLS AND FUNCTIONS
AUDIO OUTPUT
A calibrated control on the rear panel adjusts the output level
in 5 dB steps, referenced in dBu. This control knob adjusts the
absolute output level at the XLR connector. The AUDIO OUT­
PUT level control is located after the output transformer. This
allows the signal to noise ratio to remain constant regardless
of the setting of the control. As the audio level is reduced, the
noise is also reduced maintaining the same ratio.
PHASE REV
This switch reverses the polarity of the audio output signal.
The "0" setting corresponds to a positive signal at the transmit­
ter input producing a positive output on pin 2 of the XLR audio
output connector.
AC POWER SUPPLIES
The UDR200B has a universal switching power supply which
will operate on AC voltages from 95 to 240 Volts, 50 or 60 Hz.
There is no external fuse since the power supply is self pro­
tected against line transients, short circuits, and over current
conditions.
EXT DC IN
The primary purpose of this jack is to provide battery backup
in case of a loss of normal AC power. The receiver will accept
power from this jack under two conditions. The first is when­
ever the front panel power switch is in the OFF position and
the second is when the front panel power switch is in the ON
position
and the normal AC power fails or is removed. This
jack can also be used to provide normal DC power to the
receiver, if desired, although the power switch OFF position
will not function as expected. When using this jack to provide
normal DC power the receiver will always be ON regardless of
the position of the front panel power switch.
The external DC source can be 12 to 26 VDC. Pin 4 is positive
and pin 1 is ground. This jack will accept a standard 4-pin
female XLR connector. The relays and power supply stage are
fully protected by automatic reset poly fuses. The ground side
of the power supply is protected with a self resetting poly fuse
in case the UDR200B is connected to a positive ground device
through the audio cabling. The poly fuse will trip to protect the
receiver and the offending ground path can then be removed.
LecNet (RS232) JACK
This 3.5mm stereo mini jack provides the serial connection
between the receiver and the computer. A stereo mini to DB9
cable is supplied with the receiver.
ANTENNA JACKS
These are standard 50 Ohm BNC terminals for the RF input to
the receiver.
EXPANSION OUT, EXPANSION IN
These miniature jacks provide the serial port interface for
multi-channel systems in a “daisy chain” manner. The receiver
that connects to the computer uses the IN jack to receive
signals and information from the OUT jack on the next receiver
in the chain.
See the interconnect diagram on the next page.
PILOT TONE BYPASS
This switch defeats the audio output muting and triggering
action of the pilot tone. When the pilot tone is bypassed, the
Opti-Blend and the Variable Cutoff Low Pass Filter will still
provide a squelching action during weak signal conditions.
These circuits will still provide approximately 50 dB of muting
when the pilot tone is bypassed. When bypassed, a warning
message is displayed on the front panel LED character strip.
NOISE FILTER
A sophisticated dynamic noise reduction filter can be switched
to operate in two different modes. The most effective mode is
the “TRI MODE DYNAMIC”. This mode derives a signal that is
proportional to the high frequency content of the desired audio
signal multiplied by the amplitude of the desired audio signal
and divided by the RF noise level. This derived signal controls
a proportional low pass noise filter that responds to transient
high frequency signals in less than a millisecond; this speed is
commonly accepted as much faster than the human ear can
resolve. Basically, the filter gets out of the way of high fre­
quency audio information so quickly that the ear cannot detect
its operation. In addition this filter reduces high frequency
room noise and also the electronic microphone noise that is
present to some extent in all small electret microphones.
It may sound as if the filter is dulling the sound but this is a
well known psycho acoustic effect of reducing high frequency
noise. The ear is sensitized or fooled by hiss to “hear” more
high frequencies. The second mode, “LOW RF ONLY”, oper­
ates the filter only when the RF link between transmitter and
receiver is unusually weak, less than 5uV at the receiver
antennas. This is a relatively rare circumstance and so the
noise filter is effectively out of the circuit except when abso­
lutely needed.
AUDIO OUTPUT ANT B
PILOT
TONE
BYPASS
0 180
-0
-5 15
10
5
dBu
-10
-15
-20
-25
-30
-35
20
PHASE
ANT A
OUT IN
GND LIFT (RS232)
LecNet
EXPANSION
NOISE FILTER
TRI MODE
DYNAMIC
LOW RF
ONLY
90 - 240 VAC
EXT DC IN
+12 TO 26V
3
2 1
M
1
2
3
4
UDR200B Rear Panel
8