Device for realising a replacement of a bulb by means of an energy-saving illuminant for a light signal in a rail bound traffic, included in an interlocking-wise security monitoring, comprising: a) a number of illuminants, particularly LED lamps with a power supply interface, with the number of illuminants requiring less electrical power than the bulb to be replaced for generating a luminous emittance analogous to the bulb; b) an interlocking-wise interface to receive electrical power on the side of the interlocking system; c) an interface module connected between the interlocking-wise interface and the power supply interface, with the interface module: c1) comprising a control logic knowing a signal aspect and/or a characteristic line depending on the time of the day of the bulb to be replaced and that controls the power output to the power supply interface depending on the chosen signal aspect and/or the time of the day; c2) comprising a voltmeter, measuring the voltage adjacent to the interlocking-wise interface and transferring it to the control logic; c3) comprising a power consumption device shaped as a Peltier element that is thermally coupled to the number of illuminants and is controlled by the control logic dependent on the measured voltage in a way that the voltage absorbed at the interlocking-wise interface reproduces the characteristic curve of the bulb to be replaced. a) a number of illuminants, particularly LED lamps with a power supply interface, with the number of illuminants requiring less electrical power than the bulb to be replaced for generating a luminous emittance analogous to the bulb; b) an interlocking-wise interface to receive electrical power on the side of the interlocking system; c) an interface module connected between the interlocking-wise interface and the power supply interface, with the interface module: c1) comprising a control logic knowing a signal aspect and/or a characteristic line depending on the time of the day of the bulb to be replaced and that controls the power output to the power supply interface depending on the chosen signal aspect and/or the time of the day; c2) comprising a voltmeter, measuring the voltage adjacent to the interlocking-wise interface and transferring it to the control logic; c3) comprising a power consumption device shaped as a Peltier element that is thermally coupled to the number of illuminants and is controlled by the control logic dependent on the measured voltage in a way that the voltage absorbed at the interlocking-wise interface reproduces the characteristic curve of the bulb to be replaced. c1) comprising a control logic knowing a signal aspect and/or a characteristic line depending on the time of the day of the bulb to be replaced and that controls the power output to the power supply interface depending on the chosen signal aspect and/or the time of the day; c2) comprising a voltmeter, measuring the voltage adjacent to the interlocking-wise interface and transferring it to the control logic; c3) comprising a power consumption device shaped as a Peltier element that is thermally coupled to the number of illuminants and is controlled by the control logic dependent on the measured voltage in a way that the voltage absorbed at the interlocking-wise interface reproduces the characteristic curve of the bulb to be replaced.