Copyright chronologisch beginnend: Siemens Historical Institute; Hartmann & Braun AG; Siemens Historical Institute; Telefonbau & Normalzeit Lehner & Co. AG; Brown Boveri & Cie; AEG AG; Siemens Historical Institute; ABB AG; Siemens Historical Institute; AEG-Telefunken AG; Felten & Guilleaume Carlswerk AG, Brown; Boveri & Cie AG; Siemens AG; Standard Elektrik Lorenz AG; Siemens Historical Institute; ABB AG; Siemens Historical Institute; Harting Stiftung & Co. KG; Büro Prof. Dr. Edward G. Krubasik; RITTAL GmbH & Co. KG; Endress+Hauser Messtechnik GmbH & Co. KG.