An investigation into the reliability of the timing headgear.

Thirteen cervical timing headgears, then commercially available, were subjected to testing under laboratory conditions. Continuous and intermittent forces were applied, these being varied between 200 and 1000 gm. Forces were applied by attaching the cervical straps to a cylindrical drum, to activate the timer switch. Each headgear showed only moderate variation in accuracy under different phases of the testing, although timing accuracy varied considerably between individual headgears. The overall performances produced mean timing accuracy values exceeding 90 per cent in only four appliances, indicating that these 'Patient Motivators' did not provide a consistently dependable recording of headgear usage.