For Relays Or Solenoids Patents (Class 361/160)
- Code responsive (Class 361/171)
- Light (Class 361/173)
- Fluid (e.g., liquid level, humidity) (Class 361/178)
- Proximity or contact (Class 361/179)
- Frequency (e.g., audio, radio) (Class 361/182)
- Phase (Class 361/185)
- Pulse (Class 361/186)
- Voltage or current level discriminators (Class 361/187)
- Variable impedance (Class 361/188)