These additional cores can be wired into a special so-called "tamper circuit" in the alarm system. Tamper circuits are monitored by the system to give an alarm if a disturbance to devices or wiring is detected. Enclosures for devices and control panels may be fitted with anti-tamper switches. Would-be intruders run the risk of triggering the alarm by attempting to circumvent a given device. Sensors such as movement detectors, tilt detectors, air-pressure sensors, light sensors, etc., which might be employed in some burglar alarms, might also be used in a bomb to hinder defusing. Nearly all appliances and accessories can only be opened with the use of a screwdriver (or a substitute item such as a nail file or kitchen knife). This prevents children and others who are careless or unaware of the dangers of opening the equipment from doing so and hurting themselves (from electrical shocks, burns or cuts, for example) or damaging the equipment. Sometimes (especially in order to avoid litigation), manufacturers go further and use tamper-resistant screws, which cannot be unfastened with standard equipment. Tamper-resistant screws are also used on electrical fittings in many public buildings primarily to reduce tampering or vandalism that may cause a danger to others. A user who breaks equipment by modifying it in a way not intended by the manufacturer might deny they did it, in order to claim the warranty or (mainly in the case of PCs) call the helpdesk for help in fixing it. Tamper-evident seals may be enough to deal with this. However, they cannot easily be checked remotely, and many countries have statutory warranty terms that mean manufacturers may still have to service the equipment. Tamper proof screws will stop most casual users from tampering in the first place. In the US, the Magnuson-Moss Warranty Act prevents manufacturers from voiding warranties solely due to tampering. A warranty may be dishonored only if the tampering actually affected the part that has failed, and could have caused the failure. Tamper-resistant microprocessors are used to store and process private or sensitive information, such as private keys or electronic money credit. To prevent an attacker from retrieving or modifying the information, the chips are designed so that the information is not accessible through external means and can be accessed only by the embedded software, which should contain the appropriate security measures. Examples of tamper-resistant chips include all secure cryptoprocessors, such as the IBM 4758 and chips used in smartcards, as well as the Clipper chip.