SigNET’s new free-of-charge Excel based audio-frequency induction loop calculator is now online!

Utilising sophisticated formulas devised by engineers at our Research and Development Facility, the calculator helps installers determine which induction loop amplifier and cable they should use to create a BS7594 (2011) compliant AFILS installation.

The calculator is compatible with any Mac or PC computer running Microsoft Excel and is designed to work in five easy steps:

1) Enter the room length and width on the spreadsheet

2) Select/alter the number of turns in your loop (extra turns can provide increased field strength in smaller rooms and rooms with excessive ferrous metal content)

3) Select the reference level (normally -3dB but this can be reduced to -6dB – see BS7594:2011 Section 3, Table 1 Field variation in the useful magnetic field volume)

4) Set the height of measurement in metres from the plane of loop. This would be 0 if the listener is directly in line with the loop cable, approx. 1.8 for loops laid on the floor or 1.5 for ceiling mounted loops (adjust these measurements based on the actual ceiling height and typical listening height of the user)

5) Consult the wire dependent loop choice box on the spreadsheet to see exactly which amplifier and loop cable best suits your application

Says Tremayne Crossley, SigNET’s Field Sales Manager: “Our new AFILS calculator is a brilliant invention that will save you so much time and effort. The feedback I’ve had from customers who’ve trialled the software has been excellent – the overwhelming verdict is that it makes planning an installation so much easier”.


• The calculator assumes a perimeter loop is being installed in a room with very little metal content (i.e. a square or rectangular loop that is being run around the edge of the covered area).

• Although the amplifier recommended by the calculator WILL generate the required magnetic field it is the responsibility of the designer/installer to ensure the amplifier has the required inputs and features pertinent to the job in hand.

• It should be noted that steel reinforced flooring and/or roofing can considerably attenuate the field strength of the completed system – if in doubt, refer to our AFILS guide for further information.

• Prior to installation we always recommend a trial loop is run around the covered area and that the system is tested to ensure correct operation using one of our FPROK1 test kits which includes a handheld magnetic field strength meter and a handheld signal generator (c/w test tones and headphones).

Click Here to Download our Induction Loop Calculator V1.3