A-type voltage-gated potassium channel that mediates transmembrane potassium transport in excitable membranes in the brain (PubMed:15454437). Mediates A-type current I(SA) in suprachiasmatic nucleus (SCN) neurons. Exhibits a low-threshold A-type current with a hyperpolarized steady-state inactivation midpoint and the recovery process was steeply voltage-dependent, with recovery being markedly faster at more negative potentials. May regulates repetitive firing rates in the suprachiasmatic nucleus (SCN) neurons and circadian rhythms in neuronal excitability and behavior. Contributes to the regulation of the circadian rhythm of action potential firing in suprachiasmatic nucleus neurons, which regulates the circadian rhythm of locomotor activity. The regulatory subunit KCNIP1 modulates the kinetics of channel inactivation, increases the current amplitudes and accelerates recovery from inactivation, shifts activation in a depolarizing direction (By similarity). The regulatory subunit DPP10 decreases the voltage sensitivity of the inactivation channel gating (PubMed:15454437). {ECO:0000250|UniProtKB:Q03719, ECO:0000269|PubMed:15454437}. This is the function of KCND1 (potassium voltage-gated channel subfamily D member 1, ENSG00000102057).