Page 3
Doc No. DCP0000487 JH 12/7/99 rev3
Installation
Input connections
Two input connectors are standard 5 pin
Din types. Both are mic or line selectable depen-
dant upon the pin connections used, use the
following chart or see the back of the unit which
has the pin outs marked next to the relavent
connector.
Unbalanced
Balanced
line
line
pin4
signal
pin4
Hot
pin5
link to pin2
pin5
Cold
pin2
ground
pin2
ground
Unbalanced
Balanced
microphone
microphone
pin1
signal
pin1
Hot
pin3
link to pin2
pin3
Cold
pin2
ground
pin2
ground
Phantom is supplied on pins 1 and 3. 15V, 5mA
maximum per pin.
Alert input
For a simple alert signal, closing a switch
across pins 1 & 2 generates a 2KHz tone at 2Hz
on/off rate. The alert input can also be connected
to fire alarms/doorbells etc., however when con-
necting to a doorbell you must use a separate
isolated contact on the doorbell switch.
pin1
Trigger
pin2
Ground
pin3
5V
pin4
Tone in
pin5
Alert Tone.
Pins 4 & 5 must be linked at all times.
Read this manual throughally before start-
ing installation, the following procedure should
be used.
1. Install the loop (see page 6)
2. Before connecting a loop to the amplifier use a
multimeter to check the loop is not shorted to
ground at any point, (it will almost certainly
damage the amplifier if it is).
3. Connect music or speech input signal to the
amplifier. The peak line level of this signal
should be approximately 1V.
4. Ensure input levels controls and drive control
are fully anti-clockwise. .
5. Increase the input level controls until the ‘limit’
LED is just flashing. This indicates that the
dynamic range processor is receiving a signal
of the correct level. The compression ratio is
fixed at a ratio of 20:1. If you are using both
inputs the level controls act as a simple mixer.
6. Adjust the drive control until the required cur-
rent peak is produced. (see page 5). Care
should be taken when doing this to ensure
the current is within the recommended
rating of the cable. The average current
output should be approximately one quar-
ter of the maximum peak.
7. Using an induction loop receiver (eg SigNET
Rxti2), listen to the signal inside the loop. It is
also advisable to check the system with a field
strength meter. Please note that the orientation
of the field strength meter may influence the
reading.
Mains Hum
Background hum can sometimes be heard
when testing an installation especailly when test-
ing with a induction loop reciever. This is not
caused by the loop system and will NOT nor-
mally be heard by hearing aid users, due to built
in filtering in most hearing aids.
The source of mains hum is most likely to
be ( 50 Hz) mains wiring, particularly in old
buildings where Live and Neutral cables may
take different routes, thus creating an induction
loop radiating at 50Hz.
If the client complains of mains hum simply
disconnect the loop to prove that the source is
unrelated.
