Which Schuko sockets use this glow lamp?

The 5TG7304 is a replacement glow lamp for Siemens DELTA series Schuko socket outlets that include a built-in operating status indicator — a small translucent window on the socket face that glows orange when the circuit is live. Not all DELTA Schuko sockets carry this feature; only models explicitly designated with a status indicator (Betriebsanzeige) have the glow lamp socket behind the faceplate.

How do I know when the glow lamp needs replacement?

Glow lamps in mains-voltage indicators have a finite service life — typically tens of thousands of hours — after which the orange glow dims or disappears entirely. A dark indicator window on a socket that is confirmed live (tested with a voltage tester or by plugging in a working appliance) points to a spent glow lamp. The 5TG7304 plugs directly into the socket body without soldering or terminal access — remove the frame and faceplate, pull the old lamp, and push the new one in.