Page 3.1: GSM-Service-Codes for mobile phones; call forwarding, phone lock, change PIN, unlock SIM card, transfer or suppress the phone number, mailbox activation, call waiting, IMEI (International Mobile Equipment Identity).

Page 3.2: Financial Calculator; conversion of time-dependent interest rates, calculation of compound interests, instalment savings, instalment payments, depreciations (linear, progressive, declining), leasing rates, leasing costs and residual book values.

Page 3.3: The Router; function and basic settings of a router with different network clients in the private home network.

Page 3.3.1: Data Cloud; creation of an own, secure "Data Cloud" in the home network for stationary or mobile computer systems without the control of a provider.

Page 3.4: Email Account; sending emails without an own email account from freely accessible hot spots, LAN or WLAN networks in hotels and Internet cafés.

Page 3.4.1: Cryptograph; encryption and decryption of texts, programs and source codes in the scope of 3800 digits by means of a special encryption program using a public key & private key.

Page 3.5: The digital Camera; some notes on the operation and use of digital cameras.