Operation - Monacor LA-75 Bedienungsanleitung

4.1.2 Connection of the induction loop
GB
The loop amplifier must be outside the loop (⇒ fig. 3).
1) Twist the cable section between the amplifier and
the loop (⇒ fig. 3).
2) Before the induction loop is connected to the ampli-
fier, check with an ohmmeter to ensure that the loop
is not earthed.
3) Connect the cable ends of the loop, as shown in
fig. 4, to the plug-in screw terminals* (11). Tighten
the screws and pay attention to a good contact so
that no interfering contact resistances occur.
4.2 Microphones
Up to two microphones may be connected to the
6.3 mm jacks MIC IN (12, 15) of the channels INPUT 1
and INPUT 2. For INPUT 1 the microphone priority cir-
cuit may be activated (⇒ chapter 5.3).
When connecting a microphone, disengage the cor-
responding button MIC/LINE (13, 16) [position MIC].
4.3 Units with line level
Up to two audio units with line output (e. g. CD player,
cassette recorder) may be connected to the phono
jacks LINE IN (14, 17) of the channels INPUT 1 and
INPUT 2 when no microphone has yet been connected
to the corresponding channel.
When connecting a unit with line output, press
down the corresponding button MIC/LINE (13, 16)
[position LINE].
4.4 Alarm siren
The internal siren may be activated via a switch or
momentary pushbutton connected to the plug-in screw
terminals* (11) [⇒ fig. 4]. As long as the contacts are
connected, the siren sounds, the LED SIREN (1) lights
up, and the volumes of all other audio signals are auto-
matically attenuated.
4.5 Application in a PA system
1) Feed the audio signal from the PA system to one of
the line jacks INPUT 1 (17) or INPUT 2 (14). The
signal should be unbalanced, have line level, and
be independent of the volume control of the PA
amplifier.
2) Press down the corresponding button MIC/LINE
(13, 16) [position LINE].
4.6 Power supply
Finally connect a power supply unit 12 V /5 A (battery
or regulated power supply unit, e. g. PSS-5000 from
MONACOR) while observing the polarity (inside
contact = positive pole) to the power supply jack (10).
* For better handling, the terminals can be removed from their
plug-in connection.
10

5 Operation

5.1 First setting into operation
All controls are recessed against accidental misadjust-
ment and can be adjusted with a small screwdriver.
1) Prior to switching on, turn the controls INPUT 1 (5),
INPUT 2 (6), and LOOP CURRENT (9) to the left
stop for the time being.
2) Feed a signal (test signal, music piece, or micro-
phone announcement) to all connected inputs.
3) Switch on the amplifier with the switch POWER (4).
After switching on, the red LED (3) next to the
switch lights up.
4) Slightly turn up the control LOOP CURRENT (9) so
that a signal can be received in the loop.
5) Control the level of the channels to be heard with the
corresponding controls INPUT 1 (5) and INPUT 2
(6) and check the field strength in the loop with a
field strength meter. According to the European
standard EN 60118-4 a field strength of 100 mA/m
is recommended, and the maximum field strength
should not exceed 400 mA/m. Both values are re-
lated to the reference frequency of 1000 Hz. Adjust
the field strength with the control LOOP CURRENT
(9) accordingly. The 7-step LED row (2) shows the
output current. If no field strength meter is available,
the adjustment of the current can coarsely be made
by means of the following graphics and be checked
with an induction receiver (e. g. LR-200 from
MONACOR) for audio quality and receiving quality.
The required loop current depends on the size
and the width-length ratio of the loop as well as the
distance of the receiver from the loop level. With the
dimensions of the loop the required loop current
can be read from fig. 7 for a receiver distance of
approx. 1.2 m:
6
5
4
3
2
1
2 3 4
Fig. 7 Peak current in the induction loop
Example (also see fig. 3):
loop width A = 4 m
loop length B = 8 m
width-length ratio = –– = ––– = 0.5
width-length ratio A/B
5 6 7 8
loop width A [m]
A 4 m
B 8 m
0.25
0.5
0.75
1.0
9