'How to build a two valve set', No 13, Godfrey Philips cigarette card, 1925.
© Science Museum / Science & Society Picture Library
The reverse of the card reads: 'Turning grid connections. The Grid Condenser (Dubilier .0003 micro farad) is now screwed onto the baseboard between the coil holder and first valveholder. One terminal is joined to the grid terminal of the valve holder, the other to the fixed plates of the tuning condenser, and also to one side of coil holder and to aerial terminal. The other terminal of coil holder is connected to the centre (moving valves) of the tuning condensor.'