hangwaiter

hello to all, who can help me with this : I've got an electronic transformer for halogen lamps, driving a 12 volt/50 watt bulb. now i need to be able to switch my lamp between full and half light intensity. for some reasons, i can not use a heat producing resistor to lower the voltage on the lamp. Also, i can not use a dimmer on the primary side of the transformer. what can be added on the secondary side of the trafo, possibly near the bulb, to have an alternative supply of reduced voltage available on a toggle switch, so that the lamp can be switched