Disclosed is a virtually renewable electric power-generating system configured to provide an efficient means for generating electricity for charging an electrical energy storage source such as batteries using the same energy storage source to power an electro-mechanical system for generating electricity. Part of the output of the electro-mechanical system for generating electricity is fed back to the energy storage source to recharge the storage source, as well as provide energy to charge a second energy storage system.

[Problem] To provide a digital tachograph system which is inexpensive and has a system configuration easy to change and extend. [Solution] A vehicle-mounted tachograph is configured from a speed data acquisition unit (5) which is connected to a sensor (8) provided in a drive system of a vehicle, and a general-purpose terminal (4) which is a smartphone or other general-purpose portable computer capable of transmitting and receiving speed data to and from the speed data acquisition unit (5) via a general-purpose interface cable or short-distance radio communication, and the speed data at each point in time of an operation is transmitted to a management server (1) via the general-purpose terminal (4) in each transmission cycle, and recorded on a performance data file (26) stored in a storage unit (2). The contents of the performance data file (26) including three-element data are browsed on a management terminal (3) by access via the Internet (6). The general-purpose terminal (4) is removably held by a holder (7) so as not to fall during traveling.