To disable the TMS link, which you should only do if you are offline and will need to run this way for a protracted time;
Log into EPOS, then select Manager Screen

In Manager Screen, find and select Interface Manager

Find the TMSService option under the Interface column, then press the Disable button on the far right and Confirm to save the change

Success, you just severed the TMS-link between Res and EPOS. EPOS will now run in standalone mode, which allows EPOS to operate as normal, even without any active internet connectivity in the venue.
Don't forget, once your protacted downtime event ceases, you'll then need to turn this TMS-link back on again, in order to get Res and EPOS talking to each other once again.