## Common ground
All options are devices that regulate electrical parameters like voltage or current.
## Options at a glance
**8504.3X – Voltage regulators with transformers**
- **Defining trait:** Integrates a power transformer for voltage conversion and regulation.
- **Typical examples:** Transformer-based voltage stabilizers, industrial AC regulators.
- **Best fit when:** The device includes a physical transformer to step up/down voltage.
**8504.40 – Voltage regulators with static convertors**
- **Defining trait:** Combines regulation with solid-state power conversion (e.g., rectification or inversion).
- **Typical examples:** AC/DC converters with built-in voltage control, frequency inverters.
- **Best fit when:** The device converts AC to DC or changes frequency while regulating voltage.
**8511.80 – Regulators with cut-out relays**
- **Defining trait:** Includes automatic disconnection (cut-out relay) for overvoltage or fault protection.
- **Typical examples:** Overvoltage protection units, surge-protected regulators.
- **Best fit when:** The device shuts off automatically during faults or excessive voltage.
**8542.39 – IC-based voltage regulators**
- **Defining trait:** Uses a semiconductor integrated circuit (IC) as the core regulator.
- **Typical examples:** 7805, LM317, on-board microcontroller power supplies.
- **Best fit when:** The device is a small, chip-level regulator used in electronics.
**9032.89 – Automatic regulators of electrical quantities**
- **Defining trait:** General-purpose automatic control of voltage or current, often for industrial systems.
- **Typical examples:** PLC-controlled voltage stabilizers, grid-tied power regulators.
- **Best fit when:** The device is part of a larger automated system and adjusts dynamically.
## Key differences
| Option | Core Technology | Protection Feature | Integration Level | Primary Use Case |
|-------|------------------|--------------------|-------------------|------------------|
| 8504.3X | Transformer | No | Medium | AC voltage adjustment |
| 8504.40 | Static convertor | No | Medium | Power conversion + regulation |
| 8511.80 | Relay-based | Yes (cut-out) | Low | Safety-critical protection |
| 8542.39 | IC chip | No | High (chip-level) | Embedded electronics |
| 9032.89 | General automation | Varies | System-level | Industrial control systems |
## How to choose
- Does it contain a power transformer? → 8504.3X
- Does it convert AC to DC or change frequency? → 8504.40
- Does it automatically shut off during overvoltage? → 8511.80
- Is it a small chip (e.g., 7805)? → 8542.39
- Is it part of an automated industrial system? → 9032.89
## Overlaps & pitfalls
- A device with IC-based regulation and overvoltage protection could fit both 8542.39 and 8511.80.
- Some automatic regulators (9032.89) may include relays or converters, causing overlap.
- **No clear priority:** Choose based on the product’s MAIN function—e.g., if it's a chip, use 8542.39; if it protects against surges, use 8511.80