I guess we didn’t take a photo illustrating how to use the supplied mini-Toslink connector for the Dr. DAC Prime when we wrote the review.
The Dr. DAC Prime does not have a dedicated Toslink connector, because their RCA S/PDIF input doubles as a Toslink connector. Very clever indeed. Also, unlike the Dr. DAC DX2 and the AMB Gamma2 where the Toslink out only works when the digital input is through USB, the Dr. DAC Prime outputs S/PDIF through both the coaxial and the Toslink regardless of the digital input being used.
Lastly, if you choose to upsample the signal to 192kHz, then the digital out will also be 192kHz, even if your digital input signal is 44.1kHz.