Control electronics for an agricultural or forestry vehicle or an agricultural or forestry machine, having power connections at least for a first supply network (45, 46) and a second supply network (56, 57) and having at least one network connection (80), wherein the control electronics contain a communication circuit (70) which is configured to transmit data via the network connection (80) and is supplied via the first supply network (45, 46), and a logic circuit (69) which is coupled to the communication circuit (70) and has at least one control output for controlling an electrical load (84, 85) supplied via the second supply network (56, 57), having at least one switch (77) which is configured to connect the first supply network (45, 46) to the second supply network (56, 57), with the result that the two supply networks (45, 46, 56, 57) have at least one defined minimum isolation impedance in a switched-off state of the at least one switch (77), and a method for switching on such control electronics.