| General-purpose plug-in relay | Commonly 1 or 2 changeover contacts; other configurations are available. | Common versions include 12 V DC, 24 V DC, 24 V AC, 110/120 V AC, and 220/240 V AC. | Control panels, interlocking, signal switching, and general automation circuits. | Check the rated switching voltage and current for the actual AC or DC load. Resistive-load ratings should not be assumed to apply to motors, lamps, or inductive loads. | Confirm electrical endurance, dielectric properties, temperature limits, and the specified mounting and operating conditions. |
| Interface relay | Usually 1 or 2 changeover contacts, often in a compact socket-mounted format. | Frequently available with 24 V DC coils; other coil voltages depend on the model. | Isolating and interfacing PLC or controller outputs with field devices and control circuits. | Check coil operating range, input polarity where relevant, contact load rating, minimum switching load, and any suppression-device effects on release time. | Verify the relay and socket combination as a complete assembly, including terminal ratings, spacing, and installation conditions. |
| Power relay | Often 1 to 4 poles, with normally open, normally closed, or changeover contacts depending on design. | Common options include 12 V DC, 24 V DC, and mains-frequency AC coil versions. | Switching higher-current control loads, heaters, lighting circuits, and auxiliary equipment. | Use the rating specified for the particular load type. Assess inrush current, contact making and breaking duty, switching frequency, and expected electrical life. | Check rated insulation, temperature rise, endurance, and the manufacturer’s stated conditions for the declared contact rating. |
| High-sensitivity relay | Typically 1 or 2 changeover contacts, with contact form dependent on the design. | Often offered in low-voltage DC coil versions, including 5 V, 12 V, and 24 V DC. | Low-power control outputs, instrumentation, and circuits where coil power consumption matters. | Confirm coil power and pickup requirements, as well as the minimum applicable contact load. A low-power coil does not imply suitability for very low-level contact signals. | Check operating limits and electrical characteristics at the intended ambient temperature and mounting orientation. |
| Latching relay | Contact arrangements vary; contacts retain their last state after the operating pulse is removed. | Single-coil or dual-coil designs are available; supply and pulse requirements are model-specific. | Circuits requiring state retention with reduced continuous coil power, including selected control and monitoring functions. | Observe pulse polarity, pulse duration, set/reset sequence, and contact ratings. Confirm the required state after loss of supply. | Review operating and endurance tests alongside the specified set/reset conditions; do not assume behavior is identical across latching designs. |
| Time-delay relay | Commonly 1 or 2 changeover contacts; timing functions depend on the device design. | Supply options vary and may include low-voltage DC and AC versions. | On-delay, off-delay, interval, and sequencing functions in control systems. | Check the timing function, timing range and tolerance, reset behavior, and contact rating for the switched load. Timing electronics may require a specified supply waveform or polarity. | Confirm which standards apply to the complete timing relay and review its declared operating conditions in addition to elementary relay requirements. |
| Reed relay | Often one normally open contact; some designs provide changeover contacts. | Low-voltage DC coil options are common; exact values depend on the device. | Signal switching, measurement equipment, and circuits needing compact switching or electrical isolation. | Check maximum switching voltage, current, power, and load type. Account for contact bounce, sensitivity to magnetic fields, and limits on switching inductive loads. | Use the specific device ratings and test conditions; do not infer power-switching capability from the relay’s small size or low coil consumption. |
| Automotive-style electromechanical relay | Commonly normally open or changeover contacts; contact configuration varies. | 12 V DC and 24 V DC coil versions are widely used in vehicle electrical systems. | Vehicle and mobile-equipment loads such as auxiliary circuits and selected actuators. | Check DC load ratings, inrush current, inductive suppression, vibration exposure, and the voltage range expected during operation. | IEC 61810-1 alone may not address every vehicle-specific requirement; assess the additional environmental and application standards required for the end use. |