The transmitter offers a optical link (infrared) for headphones. Three infrared leds (ir) are polirised by T1 current, P1 is used to adjust the current level . Current consumption of this headphones infrared transmitter is about 60mA at 9V.
Maintain separated adapter ground and audio signal ground to prevent current reactions thru LED. The optical link is relative directional and can be improved by placing the leds in different angles and placing reflectors behind them.
The optimal input audio level is 100 – 200mV for 1.2 – 2.4 m coverage of this headphones ir transmitter. On the site we provide the infrared receiver schematic for this infrared headphones transmitter.