WL-19 and WL-20 RF Manual
https://www.binmaster.com/amfile/file/download/file/1300/product/4271/
WL-19D RF Modem Manual
https://www.binmaster.com/amfile/file/download/file/1301/product/4269/
WL-19 and WL-20 RF Manual
https://www.binmaster.com/amfile/file/download/file/1300/product/4271/
WL-19D RF Modem Manual
https://www.binmaster.com/amfile/file/download/file/1301/product/4269/