The input device name can be obtained using arecord -L. The sox call is required to strip one of the channels (use remix 2 to select the right channel).
arecord -D "hw:CARD=PCH,DEV=0" -c 2 -r 44100 -f S16_LE -t raw - | sox -t raw -r 44100 -e signed-integer -b 16 -c 2 - -t wav - remix 1 | minimodem -r 1200 -S 1200 -M 2400 --startbits 1 --stopbits 2 -f - | hd