Apparatus , comprising: a catheter ; an electrode positioned on the catheter; a display screen upon which is presented a graphical image of a heart of a patient, including icons representing the catheter that is positioned within the heart and the electrode , while the electrode is in contact with tissue at a location in the heart; and user controls configured to be used by a user to communicate with a processor , wherein the processor is configured to: display, on the display screen , a selection menu comprising a plurality of signal types, receive, via the user controls , selection of a first signal type of the plurality of signal types from the selection menu and register at least one predefined signal feature of the first signal type, acquire, using the electrode , electrical signals from the tissue at the location, process the acquired signals so as to detect an occurrence of the at least one predefined signal feature in the acquired signals, and upon detecting the occurrence of the at least one predefined signal feature, modify a visual feature of at least one of the icon representing the electrode and the icon representing the catheter on the display screen , wherein the at least one predefined signal feature comprises a morphological feature of the signal and/or a temporal feature of the signal. a catheter ; an electrode positioned on the catheter; a display screen upon which is presented a graphical image of a heart of a patient, including icons representing the catheter that is positioned within the heart and the electrode , while the electrode is in contact with tissue at a location in the heart; and user controls configured to be used by a user to communicate with a processor , wherein the processor is configured to: display, on the display screen , a selection menu comprising a plurality of signal types, receive, via the user controls , selection of a first signal type of the plurality of signal types from the selection menu and register at least one predefined signal feature of the first signal type, acquire, using the electrode , electrical signals from the tissue at the location, process the acquired signals so as to detect an occurrence of the at least one predefined signal feature in the acquired signals, and upon detecting the occurrence of the at least one predefined signal feature, modify a visual feature of at least one of the icon representing the electrode and the icon representing the catheter on the display screen , wherein the at least one predefined signal feature comprises a morphological feature of the signal and/or a temporal feature of the signal. display, on the display screen , a selection menu comprising a plurality of signal types, receive, via the user controls , selection of a first signal type of the plurality of signal types from the selection menu and register at least one predefined signal feature of the first signal type, acquire, using the electrode , electrical signals from the tissue at the location, process the acquired signals so as to detect an occurrence of the at least one predefined signal feature in the acquired signals, and upon detecting the occurrence of the at least one predefined signal feature, modify a visual feature of at least one of the icon representing the electrode and the icon representing the catheter on the display screen , wherein the at least one predefined signal feature comprises a morphological feature of the signal and/or a temporal feature of the signal. <EOS>