 The receiving apparatus reproduced the transmitted image by means of paper impregnated with potassium ferricyanide, which darkened when an electric current passed through it from the synchronized stylus.In operation the pantelegraph was relatively slow; a sheet of paper 111 mm × 27 mm, with about 25 handwritten words, took 108 seconds to transmit.The most common use of the pantelegraph was for signature verification in banking transactions.