The latest acquisition in my grotto is an IFR 2843, which was badged as a BT Tester 455D when supplied to Beattie for her technicians to use.
The company IFR is no more. It was first absorbed into the Aeroflex Corporation as a division operating under the IFR name and then, once the profitable products had been moved around the parent company, it was terminated.
I have been in contact with Aeroflex and they have explained that although the IFR 2843 is no longer available to purchase, it is still supported -- for repair and calibration -- by Aeroflex in Europe. The European office very generously provided me with copies of both the User and Maintenance Guides in PDF format.
Does any fellow Kitizen recognise the device or, more interestingly, has had experience of using one?