Counter-Surveillance & TSCM

Counter-surveillance gear answers one question: is something in this room listening or watching? The honest version of the answer is that equipment finds part of the problem and trained search finds the rest.
What is here. RF detectors and spectrum analysers, camera-lens finders, non-linear junction detectors, pole cameras and inspection tools, noise generators for masking a conversation, and complete TSCM kits.
What detection can and cannot do. An RF detector finds a transmitter that is transmitting while you are standing there. It will not find a device recording to internal storage, a hardwired microphone, a device that is switched off, or one that transmits in short bursts at a time you are not sweeping. Lens finders find optics pointed at you, which is the one class of device that does not need to transmit at all. That is why a real sweep combines RF work with physical search, junction detection and inspection of wiring and telephony.
Using it well. Turn off the known transmitters first — phones, laptops, smart TVs, printers, access points — then sweep, then re-sweep with the room in normal use. Work slowly and close to surfaces; near-field detectors lose signal quickly with distance, which is what lets you localise a source. Expect false positives and work by elimination.
One caution. If you believe you are actually being monitored, rather than testing your own gear, a partial sweep can tip off whoever placed the device and cost you the evidence. That is the point to stop and bring in a licensed team: technical surveillance countermeasures, which ends in a written report you can act on.