'How to build a two valve set', No 25, Godfrey Philips cigarette card, 1925.
© Science Museum / Science & Society Picture Library
The reverse of the card reads: 'The set finished. The three short leads of the battery cable go to the High Tension battery. The brown wire to the negative (-), the green to 60, and the gold to the highest number (100 to 120), according to the size of the battery in use. The local station and 5XX will come in at fair loud speaker strength and over a dozen distant stations have been logged in as many minutes.'