When you charge the transmitter (WL-T) by connecting it to the TRANSMITTER jack on the receiver (WL-50), the receiver must be on. Connect an AC adaptor (PSA series) to the IN jack, connect a cable to the OUTPUT jack to turn on the power, then charge the transmitter.
In case the BATTERY indicator blinks red and the battery cannot charge, a charging error may have occurred. If the BATTERY indicator blinks red, refer to the "Troubleshooting" section in the WL-50 Owner's Manual for more information.
If you use the WL-50 for the first time or have not used it for a long time
The transmitter may be completely discharged. The transmitter in a discharged state does not charge through the TRANSMITTER jack on the receiver (WL-50). Use a commercially available USB cable (USB micro-B type) to charge the battery fully.
Charging from a USB AC adaptor: Connect a commercially available USB cable and USB AC adaptor (5 V/0.5 A or higher) to the DC IN 5 V port.
Note: When charging from the DC IN 5 V port, the wireless connection does not operate.