RELEI VAQT, releest, ki tahvili tasirotro az yak uzv ba digar uzvi olati avtomati yo az yak olat ba olati digar ba muhlati matlub takhir dihad. Relei vaqt asosan az qismqoi tasirpazir (hangomi omadani signal relero ba kor meandozad), takhirdihanda (taqvili signalro ba muhlati matlub nigoh medorad) va ijrokunanda (tasirotro ba obekti idorashavanda meguzaronad) iborat ast. Relehoi usuli takhirandozashon elektri, pnevmatiki, magniti, mekhaniki, elektromekhaniki, termiki va gidravliki mavjudand. Relei vaqtro beshtar dar dastgohhoi avtomati istifoda mebarand.