5
For maximum flexibility, the signal heard in the headphones is post filter. This
provides re-assurance that the correct measurement is being made, and can help
with diagnosis of any problems.
Note: Headphones will be muted when >+8dB / >-12dB LED illuminates.
SIGNAL CABLES
In order to test / commission an induction loop system using the CD provided you will
need to interface a CD player to an appropriate input of the system.
Most portable CD players will have a headphone output which can be used, and
other equipment is likely to have a pair of phono outputs. Either way, care must be
taken when feeding into a mono (single channel) input that both left and right stereo
signals are summed / scaled correctly using appropriate resistors. The table below
should provide a solution to the majority of inputs, but if in doubt contact Ampetronic
for advice at
These connections can be made using Ampetronic SCC (Signal Connection
Cables) a kit of cables facilitating connection of most audio systems to most
induction loop systems. Please contact Ampetronic or consult
www.ampetronic.com
for details.
Input type
Connector, pins & wiring
Connection requirements
Electrect
microphone
i/p
2-pole
jack
Tip
Hot
Left and Right channels summed through
two 10k
Ω
resistors using screened cable:
Sleeve
Cold
Balanced
microphone
i/p
(phantom
power off)
XLR
X pin 1
Cold
L pin 2
Hot
R pin 3
Cold
Unbalanced
line level i/p
(mono)
2-pole
jack
Tip
Hot
Left and Right channels summed through
two 1k
Ω
resistors using screened cable:
Sleeve
Cold
Balanced
line level i/p
(mono)
3-pole
jack
Tip
Hot
Ring
Cold
Sleeve
Cold
Low Z
speaker i/p
Bare wire
termination
Polarity is not
important for
floating inputs.
Unbalanced
line level i/p
(stereo)
Twin
phono
Left and Right
have a separate
cable each.
Direct connection through
standard cables.
100V
speaker i/p
N/A
A CD player cannot produce
these levels, and the best
solution is to feed into the
speaker system itself.
Note: It is possible to test a system by connecting only one channel (left or right) of the CD to the
equipment. This will not be a problem with the FSM test signals disk as both channels (Left and
Right) are identical.
In
p
u
t
R
L
COLD
HOT
S
te
re
o
s
o
u
rc
e
In
p
u
t
S
te
re
o
s
o
u
rc
e
100
Ω
R
L
HOT
COLD