Abstract: A signal splitter includes a low-pass filter circuit for permitting a low-frequency component of an incoming signal in an incoming telephone line coupled to a first connecting port to pass therethrough to a second connecting port, and a coupling circuit including a capacitor coupled between a first terminal of the first connecting port and a second terminal of the second connecting port, and a coupling transformer having a primary winding that interconnects the first terminal of the first connecting port and a first input end of the low-pass filter circuit, and a secondary winding that interconnects the second terminal of the second connecting port and a second output end of the low-pass filter circuit.

Abstract: A method for controlling the color contrast of a multi-wavelength light-emitting diode (LED) made according to the present invention is disclosed. The present invention includes at least the step of increasing the junction temperature of a multi-quantum-well LED, such that holes are distributed in a deeper quantum-well layer of the LED to increase luminous intensity of the deeper quantum-well layer, thereby controlling the relative intensity ratios of the multiple wavelengths emitted by the LED. The step of increasing junction temperature of the multi-quantum-well LED is achieved either by controlling resistance through modulating thickness of a p-type electrode layer of the LED or by modifying the mesa area size to control its relative heat radiation surface area.