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Design Responses > About Locks > Case Studies >
SGLocks - Alarmed Locks

The Tough Stuff and Street Safe locks are D-lock variants with integrated alarms that emit a high frequency/high volume siren when force is applied to them. SG locks also offer a ‘Heavy Security’ padlock that also houses an alarm.

Should a thief try and break the lock the alarm will activate alerting bystanders of a thief’s presence and actions. If thieves were to become familiar with the appearance of these locks then applying one to your bike could reasonably be expected to work as a deterrent. The Tough Stuff lock is the heavier and more secure of the two D-locks, it is designed to lock both the wheel and frame of a bike to a parking stand. The Street Safe lock is lighter and intended to be used as a secondary lock to secure the front wheel of a bike to the bike frame. The Heavy Security padlock can be used with a shackle chain or cable for added security.

In both products, the siren is housed in the body of the lock. Once the alarm is set it activates a smart chip, which can detect different degrees of force. The alarm has a tolerance to a certain degree of force to avoid false alarms. Once this ‘trigger force’ is exceeded a 100db alarm will sound. The alarm will continue to sound until the lock is left undisturbed for at least 35 seconds.

The alarm runs off six replaceable LR44 batteries. When the batteries are running low the lock ‘bleeps’ to let you know. The batteries are easy to replace.

Alarmed D-lock / padlock.

£19.99 – £39.99.


Sold Secure Rating

The Tough Stuff is constructed from a 14mm hardened steel shackle head while the body is made from high-grade cast steel. The Heavy Security padlock is made from 12mm hardened steel.

• The alarm brings unwanted attention to a theft in progress and could come to act as a visual deterrent to thieves
• Alarm is activated before the lock is broken – not after!
• Vinyl coating protects bicycle frame from damage

• Cycilsts would require both locks to alarm and secure both wheels and the frame of their bike to a stand
• No bracket is provided to attach the lock to the bike, although the manufacturer believes that such mounts are of limited use and therefore does not supply them
• May be activated accidentally causing embarrassment and ‘alarm’ fatigue – where people get used to hearing alarms activated, thus reducing their deterrent value


©2008 // DESIGN AGAINST CRIME RESEARCH CENTRE // LONDON WC1B 4AP fully funded by the AHRC / EPSRC Designing for the 21st Century Initiative