The Panasonic AQY210HL is a PhotoMOS solid-state relay from the AQY series — a MOSFET-output optocoupler that switches AC or DC loads without mechanical contacts. The SPST-NO (1 Form A) circuit closes when the input LED sees 1.14 VDC typical, and the output handles 0 V to 350 V at up to 120 mA continuous. The 25 Ohm max on-state resistance means the relay dissipates about 0.36 W at full load — the 4-DIP through-hole package sinks that through the PCB copper, so a standard FR4 layout with no heatsinking is fine for this current level.
The 120 mA load current and 350 V blocking voltage cover most low-power signal switching — think sensor outputs, valve solenoids under 3 W, or PLC digital outputs driving small contactors. The AC/DC output type means the internal back-to-back MOSFETs conduct in both polarities, so polarity-sensitive loads like DC coils need the same wiring discipline as a mechanical relay. The PC pin termination matches standard 0.100-inch pitch DIP sockets or solders into plated through-holes on a single-sided board.
The 4-DIP (0.300-inch, 7.62 mm) package is the standard narrow-body DIP footprint — 7.62 mm row spacing, 2.54 mm pin pitch. Through-hole mounting keeps the relay mechanically secure in high-vibration environments where a surface-mount SSR might crack solder joints.
The base product number AQY21 covers the family, and the HL suffix denotes the tube packaging variant.