This application note describes the MAX7461 loss-of-sync alarm, which provides composite sync detection in National Television System Committee (NTSC), Phase Alternating Line (PAL), and SECAM (Séquentiel couleur à mémoire) applications. This device is simple to design and quickly detects the presence or loss of sync within a few lines. The MAX7461 also has the capability to differentiate between standard-definition television (SDTV) and high-definition television (HDTV) syncs. It therefore provides a complete solution for detecting the presence or loss of sync with no external components. This enables a system processor to rapidly determine if video signals with valid syncs are present without the overhead of software polling and processing of one or more video inputs.