The R-44 manual says to use a mini-TRS cable (male to male 1/8" stereo cable), which is generally not described as a coax cable.
Once linked and set to master at one end and slave at the other, the pair of recorders will make clock-synchronized recording of up to 8 channels, according to the manual. The master machine controls record start, record standby and record stop on the slave.
This scheme is different than the SMPTE time code sync that's available on
the Edirol R-4 Pro, Sound Devices 702T and other more expensive recorders. SMPTE time code is used to sync the recorder with a video
camera's frame rate.
Flintstone