ET120 & ET60 Installation & Maintenance Manual
Final Setting
Using the ETFSM held vertically and at the listening height (ear level) loop users will be at (standing or
sitting), measure the field strength in the centre of the room. This should be 0dB peaking at +3dB when
the limit LED blinks, if this is not the case adjust the drive control on the amplifier to achieve this level.
Finally walk through the area covered and note the average level of the loop field, adjusting the loop
amplifier if necessary so that the average field strength is between -3dB and +3dB over as much of the
area as possible. It is also wise to mark on a plan, areas of poor coverage or high background noise so
hearing aid users can be directed away from these areas.
Metal Loss Adjustment
Once commissioned, we recommend listening to the loop signal with a receiver such as the ETRX to
gain a qualitative measurement of loop audio performance, if the high frequencies are severely
attenuated slowly turn the metal loss correction pot clockwise until the high frequencies are restored.
It may be wise to supply the responsible person a loop receiver so they can periodically measure loop
operation and record this in a logbook.
Technical Specification (values for ET60 in brackets)
Inputs
Audio inputs
1 off balanced mic or unbalanced mic, 1
off 100V line or balanced line selectable.
Type
2-part 5mm Screw terminals
Line Power
Aux 12V 100mA for loop OK signs and
input pre amplifiers
Phantom 12V
2mA
Sensitivity
-50dBV Microphone, +40dBV 100V line,
-10dBV balanced line.
Mains Input
Voltage
230V ~ 50/60 Hz
Current
250mA Nominal (180mA)
Power
90VA Max (60VA Max)
Internal fuses
Mains 1A (F) HBC
Fuse for Spur
3A
Indication & Controls
LED indicators
1 off input signal limit, 1 off AC present,
4 off loop current 1A, 2A, 3A, 4A (0.8A,
1.5A, 2.2A, 3A)
User Controls
2x input mixer, Metal loss adj
current Drive.
ust and
Options
Protection Recessed
screwdriver adjust only.
Audio Processing
Metal Loss
0 to 3dB per Octave
Compressor
Variable ratio 1:1 to limit 20:1.
Attack
10mS
Release
Automatic from 500mS to 1500mS
Dynamic Range
>60dB
THD
<0.25%
Output Stage
Type
Current
Mode
Loop impedance
0.1
Ω
to 2
Ω
max 3
Ω
@1.6KHz
Loop Type
Single turn 1mm to 1.5mm CSA
(0.75mm to 1mm CSA)
Peak Current
>8A peak (>6A peak)
125mS burst
>4A peak (>3A peak)
RMS Current
2A @1KHz (1.8A @1KHz)
Protection
DC, Thermal, Short circuit, soft start.
Dimensions
Extents Height
225mm
Width
160mm
Depth 80mm
Weight 1.2Kgs
(1Kgs)
Mains Supply
110V operation
The ET60 & ET120 Units are designed and manufactured in the UK by:
Current Thinking Ltd,
Unit 91 Silver Briar
Enterprise Park East,
Sunderland,
SR5 2TQ.
www.current-thinking.com
Document DCC ET12 7001-03 Rev 1 Aug 2005
Page 8 of 8
