ALT 72 ASSISTIVE LISTENING TRANSMITTER
INPUT LEVEL
7
+
OFF L C+L
CHANNEL
POWER
MODULATION
LIMITING/
COMPRESSION
1
0
2
3
4
5
6
7
8
9
10
2 Front Panel Controls and Indicators
1 2 3 4 5
1. INPUT LEVEL CONTROL - This control is used to
adjust input sensitivity. It should be set at or just below
the point where the modulation indicator lights on audio
peaks.
2. MODULATION INDICATOR - Lights to indicate that
full modulation is being reached when the LIMITING/
COMPRESSION switch (see Item 3) is set to “OFF”.
With the switch set for either the “L” or “C+L” position,
this indicator will light on audio signal peaks as the
limiter is activated at full modulation level. Also see
Item 3 for additional hints for proper setting of the
LIMITING/COMPRESSION switch for a given type of
audio source.
3. LIMITING/COMPRESSION SWITCH - This switch
selects the operation of the limiter. Select the proper,
or desired, setting according to the following criteria:
“OFF” - For audio sources with limiting and/or
compression already applied. This setting bypasses
the limiting circuitry of the ALT 72. With the audio
source connected, adjust the INPUT LEVEL control to a
setting at or just below the point where the
MODULATION indicator lights on audio peaks.
“L” - For most types of audio sources and listening
environments. This setting provides automatic limiting
on audio peaks to prevent loud bursts and to avoid over
modulation conditions which can cause distorted audio
at the receiver. With the audio source connected,
(for example, the output of a public address amplifier
with a person speaking at a normal level into the
microphone), adjust the INPUT LEVEL control to a
setting at the point where the MODULATION indicator
lights on audio peaks.
“C+L” - For audio sources that contain relatively low
audio levels combined with relatively high audio levels
as might be encountered when the audio output from a
public address amplifier contains audio from multiple
microphones with different persons speaking.
This setting provides automatic increasing of the low
level audio passages combined with limiting on voice
peaks. This type of audio processing can sometimes
aid intelligibility for a person receiving the signal while
located in a relatively noisy audio environment. With
the audio source connected, and the weaker audio
levels active, adjust the INPUT LEVEL control to a
setting at or just below the point where the
MODULATION indicator lights on audio peaks.
4. CHANNEL SWITCH - Used to select transmitted
frequency. Frequency assignments are as follows:
CHANNEL
FREQUENCY
0
72.1 MHz
1
72.3 MHz
2
72.5 MHz
3
72.7 MHz
4
72.9 MHz
5
74.7 MHz
6
75.3 MHz
7
75.5 MHz
8
75.7 MHz
9
75.9 MHz
This table also appears on the bottom of the unit.
5. POWER INDICATOR - With the AC Adapter
connected to the ALT 72 rear panel DC Input and the
AC Adapter plugged into an AC power source, this LED
lights when the rear panel POWER switch is set to the
"ON" position.
