A D.C. lamp system having a number of small zener diodes arranged in eleccal parallelism with various lamp current supply wires. The zener diodes are sized so that the collective wattage ratings of the zeners is equal to the arithmetical product of the D.C. supply voltage and the summation of the safe amperages of the lamps in the system. In event of normal lamp burnout, any tendency of the other lamps to also burn out due to excessive current surge is countered by the action of the zener diodes; potential excess current is drained through the zener diodes to ground. A large number of small zener diodes are used in preference to one large zener diode, thereby minimizing the need for heat sinks or special cooling means required by a larger zener diode.