An apparatus includes a sensing unit and control circuitry. The sensing unit is connected to a channel that delivers Electro-Physiological (EP) signals from a cardiac catheter to an EP recording system and pacing signals from the EP recording system to the catheter. The sensing unit is configured to automatically identify time intervals during which the pacing signals are delivered. The control circuitry is configured to route the EP signals on the channel from the catheter to the EP recording system via an intervening system that is detrimental to the pacing signals, to switch the channel to an alternate path that bypasses the intervening system during the identified time intervals, and to route the pacing signals from the EP recording system to the cardiac catheter over the alternate path.