Telephone pair; No 3712 & 3752

After the telephone was patented in 1876, this new communication technology spread like lightning. In order to demonstrate these recent developments in his physical lectures, Elisa van der Ven (1833-1909), conservator of the Physical Laboratory of the Teylers Museum since 1879, acquired nearly all telephone devices then available on the market. Among them was also this set of ‘butterstamp’-home telephones, which were made by the German firm of Siemens & Halske as from 1878. To let the telephone ‘ring’, each device contains a ebonite whistle, which can make the membrane of the microphone vibrate heavily. As a result a current pulse is sent to the receiver. The bang that is produced will draw the attention of the conversation partner. Then a normal conversation can be held via the horns.