The P-04 is used in conjunction with the TD-53 for detecting carrier current transmitters and concealed video cameras. Examples of carrier current transmitters are the wireless intercom and room monitors sold in many electronic stores and catalogs.

Carrier current eavesdropping devices can be connected to power lines, phone lines or other wire pairs. The probe covers from 10 KHz to 600 KHz in two ranges. It uses a directional pickup loop and no connection to the power lines or other wires under test is necessary. Any demodulated audio is fed to the TD-53 for monitoring and verification purposes.