What the 1.25 A and 60 V ratings mean for your BOM
The AQY212G2SX is a PhotoMOS™ solid-state relay from Panasonic's AQY series, switching AC or DC loads up to 1.25 A continuous and 60 V peak. The 500 mOhm max on-state resistance sets the conduction loss — at 1.25 A the dissipation is roughly 0.78 W, which the 4-SOP package must sink through the board copper.
Surface-mount package and board integration
Housed in a 4-SOP (0.173", 4.40 mm body) with gull-wing leads, the AQY212G2SX sits in a standard surface-mount footprint. The SPST-NO (1 Form A) output is a single normally-open contact, so the relay closes when the input LED is forward-biased. The 4-SOP package is common across the AQY family, making it a drop-in fit for existing layouts that already use this footprint.