Pore-forming subunit of the rod cyclic nucleotide-gated channel. Mediates rod photoresponses at dim light converting transient changes in intracellular cGMP levels into electrical signals. In the dark, cGMP levels are high and keep the channel open enabling a steady inward current carried by Na(+) and Ca(2+) ions that leads to membrane depolarization and neurotransmitter release from synaptic terminals. Upon photon absorption cGMP levels decline leading to channel closure and membrane hyperpolarization that ultimately slows neurotransmitter release and signals the presence of light, the end point of the phototransduction cascade (By similarity) (PubMed:34699778). Pore- forming subunit of the olfactory cyclic nucleotide-gated channel. Operates in the cilia of olfactory sensory neurons where chemical stimulation of the odorant is converted to an electrical signal. Mediates odorant-induced cAMP-dependent Ca(2+) influx triggering neuron depolarization. The rise of intracellular Ca(2+) levels potentiates the olfactory response by activating Ca(2+)-dependent Cl(-) channels, but it also serves as a negative feedback signal to desensitize the channel for rapid adaptation to odorants (By similarity). Conducts cGMP- and cAMP-gated ion currents, with permeability for monovalent and divalent cations. The selectivity for Ca(2+) over Na(+) increases with cGMP concentrations, whereas the selectivity among monovalent ions is independent of the cGMP levels (By similarity) (PubMed:34699778). {ECO:0000250|UniProtKB:A0A8I5ZN27, ECO:0000250|UniProtKB:Q28181, ECO:0000250|UniProtKB:Q9NQW8, ECO:0000269|PubMed:34699778}. [Isoform GARP2]: High affinity rod photoreceptor phosphodiesterase (PDE6)-binding protein that modulates its catalytic properties: it is a regulator of spontaneous activation of rod PDE6, thereby serving to lower rod photoreceptor 'dark noise' and allowing these sensory cells to operate at the single photon detection limit. . This is the function of Ensembl gene identifier ENSG00000070729 (CNGB1, cyclic nucleotide gated channel subunit beta 1).