'How to build a two valve set', No 7, Godfrey Philips cigarette card, 1925.
© Science Museum / Science & Society Picture Library
The reverse of the card reads: 'Fixing reaction condenser. This small variable condensor has a capacity of .0001 micro farad and is made by Mesrs. Ormond Ltd. It is fixed in a similar manner to the tuning condensor. The control knob, which has a pointer fixed to is, is secured on the spindle by a grub screw, which is tightened up by screws as shown. The instrument has two sets of fixed vanes, these should be connected together with a length of tinned copper wire, as is used to wire up the other components, the two ends being secured under the nuts which hold on the end plate.'