Unlike many other switches used in domestic, industrial or commercial settings, key switches can only be actuated with the use of a physical key, as opposed, say, to a hand-operated toggle, rocker, push-button, handle or code (a standard car ignition control is one of the most ubiquitous forms of key switch).

Although keyless ignition technology is gaining in popularity, the crucial point is that a piece of equipment, machinery or circuitry controlled by means of a key switch can only be accessed by designated key holders. Whereas rocker switches and toggle switches, for example, can be actuated by anyone who passes by, key switches introduce a layer of security and restricted access. Each key switch will have only one bespoke key that fits it and will not function if the wrong key is inserted: the key must be turned in the switch to operate the equipment or machinery and if the wrong key is used, no rotation will be permitted.


The basic “warded lock” design of the key switch (see below under technical aspects) has been in existence since at least the middle ages, during which they were widely deployed in labyrinthine buildings such as monasteries, where their design complexity grew and grew. They began to be used widely in complex industrial and manufacturing settings in the twentieth century to control expensive or potentially hazardous machinery and equipment which required restricted access for safety and security. Their use continues to this day in these applications, although as digital and electronic key switches begin to be developed, they may be progressively replaced. However, they remain popular for these applications largely because they remain considerably less costly than electrical alternatives.

Technical aspects

Until relatively recently, traditional metal keys with specific sequences and depths of notches cut into one or both edges have been used to operate key switches. Very similar to traditional locks, the notches precisely match the pattern of wards or obstructions within the key switch, so that provided the right key is inserted, it will rotate freely within the lock. This enables relatively high levels of security through access restriction, as only exactly the right keys (or specially designed master keys which have been fashioned to operate several different switches) will turn the switch mechanism.

Electronic key switches are progressively gaining ground as an alternative to the mechanical variety. A particular key can be assigned to a particular human operative, enabling companies to monitor when switches are being activated and by whom. At this stage of development, however, they are considerably more expensive than their mechanically-operated counterparts.

For machinery requiring especially high levels of restricted access, an additional unique key switch can be installed. Some forms of military armaments require this kind of security, along with equipment controlling potentially dangerous operations: the device or equipment will require both switches to be actuated, with each switch requiring a unique key, both of which will have been assigned to different human operatives. Double switch security of this sort may require simultaneous actuation to operate the device or equipment, or they may be configured to operate only when actuated in sequence.

Product application - where the key switch is used in manufacturing – any famous instances?

Typically, key switches are used on either exceptionally expensive or potentially dangerous pieces of equipment or machinery in industrial and manufacturing settings. Machines used for critical operations are frequently activated and deactivated by means of key switches. They circumvent the inherent limitations of push-switches, rocker-switches and other mechanically-actuated switches which can be accidentally bumped or pressed, ensuring that only intentional actions are carried out by operatives in relation to the machinery or equipment they control.

They are especially suited to complex machines which require considerable amounts of time to initiate or shut down, as well as machines controlling critical processes such as the electrical power or air filtration in a manufacturing plant.

How the key switch differs from other switches

Essentially, key switches are designed to be tamper-proof and accident-proof. Other mechanically actuated switches can easily be accidentally (or mischievously) actuated by being deliberately or inadvertently tripped. The key switch requires the operative to insert precisely the right key into its mechanism and rotate it, introduce a strong element of deliberate intentionality into the operation of the equipment or machinery controlled by the switch. Because of this, it tends to be installed on equipment and machinery requiring restricted access: only the appropriate key will result in the activation or deactivation of the device controlled by the switch, and keys can be assigned to designated personnel for heightened security.

Current product advantages and limitations

Key switches are especially useful in environments where restricted access to expensive or potentially hazardous machinery or equipment is necessary. Because they require operatives to insert a physical key and will not turn if the wrong key is inserted, they minimise the risk of accidental or mischievous equipment activation or deactivation.

Where necessary, suitable alternatives

As previously mentioned, electronic key switches are gaining traction, offering a rapid and relatively straightforward means of assigning specifically-coded keys to specific individuals, Mechanical, warded lock-type key switches remain more prevalent, however, as they are considerably less expensive and yet deliver the increased security very reliably.