Document No DCP0002129 TC 26/03/02 Rev 4
Page 6
PDA200E Induction Loop System -
Installation Guide
2 m
2 m
0.75 m
Loop Amplifier
Overall length
Overall
width
The amplifier may be connected
to any point on the loop
Installing the Loop Cable
The loop cable should be laid in a single turn and wired into the Termination block as shown in the diagram
on page 2 of the manual.
In the vast majority of cases loop cables are normally mounted horizontally around the perimeter of the room
to be covered, either at ceiling or floor height. They may also be installed under carpet by using flat loop
cable.
Do not install the loop cable closer than 1.2M to a hearing aid position
Overspill and more complex installations
The magnetic field is not confined to the area
within the loop and the signal may be heard in ad-
jacent areas such as a corridors and up to three
times the width of the loop away.
If this is a problem there are special designs of
loop that can reduce the overspill field.
The AFILS British Standard (BS 7594) suggests
several technically complex solutions that are
reasonably effective but are rarely employed due
to high cost.
A low-cost but effective method to reduce overspill
is to make a smaller loop, typically in the centre of
a room. The smallest practicable loop for floor or
ceiling mounting (up to 3 metres high) is 2 metres
square. This will provide a reasonable field at head
height above the loop and up to four metres away
in all directions.
This loop may be installed above a suspended
ceiling or in plastic conduit in the floor. Flat cable
may be used under carpet.
In larger installations overspill can be reduced by
laying the loop in an ‘electric grill’ pattern. Each
pattern can be considered as a many pronged fork.
The pattern should be spaced approx. 2m from the
nearest wall / next pattern, prongs of the fork should
be spaced approx. 2m apart and should be approx.
2m wide, prongs should extend approx. 0.75m off
the base of the fork.
If the loop user is confined to a bed (for example in
a hospital or a nursing home) then the loop pattern
should take into account the position of the user and
the field strength of the loop and a loop pad may be
the simplest solution.