Reed relays (also known as reed switches) are a type of electromechanical switch that utilizes a conductive reed contact instead of an armature to switch the current path. They are activated by an externally provided magnetic field from a solenoid or permanent magnet, and are commonly used as proximity sensors in applications like burglar alarms and tamper-proofing circuits.

Reed relays are typically hermetically sealed, enabling operation in moist and dusty environments. The switching mechanism provides galvanic isolation between the control circuit and the switched current path. Reed relays also exhibit low short circuit impedance, relatively high operating speed (typically around 1mS) and have high reliability. Although faster than other electromechanical relay types, a reed switch cannot handle a significant amount of current or voltage through its contacts.

Important specifications include maximum DC switching current, maximum voltage, typical series impedance, maximum power dissipation and isolation. Essential specifications include the minimum activation magnetic field strength that the reed switch requires to close and the maximum field strength present for the relay to be reliably open circuit.