What the 600 V / 50 mA rating means on a signal relay
The AQY216EH is a PhotoMOS™ solid-state relay from Panasonic's AQY series, switching AC or DC loads up to 50 mA across a 0 V to 600 V range. That 600 V ceiling is unusual for a signal relay — it covers telecom ring voltage, 480 VAC line monitoring, and high-side battery stack sensing without an external voltage divider. The SPST-NO (1 Form A) output is a normally-open MOSFET pair, meaning the relay closes when the input LED is forward-biased at 1.14 VDC typical. The 120 Ohm on-resistance (max) sets the voltage drop at full load: 6 V across the output at 50 mA, which matters if the downstream circuit has a tight supply headroom.
Housed in a standard 4-DIP (0.300-inch row spacing, 7.62 mm pitch) through-hole package, the AQY216EH mates with a 0.100-inch grid PCB layout. The PC pin termination is wave-solder compatible, and the 4-DIP outline is a drop-in replacement for many mechanical reed relays in the same footprint — no board spin needed if the existing layout has the same pinout.
Listed as Active by Panasonic Electric Works — this is a current-production part, not an NRND or EOL line.