1: Unambiguity. The signal must mean Pay attention to your awareness now! and nothing else. For example, a telephone ring is not adequate.
2: Easy detectability. The user must not have to struggle to discern whether the signal exists or not.
3: Rapid onset. The object is to designate with precision exact moment under investigation. For example, that makes phone vibrating alerts not adequate.
4: Privacy. The signal should not disrupt others in the vicinity.
5: Portability. The signal should be able to follow the subject easily to wherever that experience takes place.
At left is the beeper used in the Descriptive Experience Sampling studies conducted by Dr. Hurlburt and his colleagues.
Specifications
The random interval generator v.3.x. creates either random or fixed intervals that are terminated by audible beeps. The beep is a 700hz tone that is delivered through a switchable onboard speaker or an external earphone, both controlled by a volume control. Random-interval or fixed-interval mode is selected by a switch inside the case. The interval lengths are easily programmable by switches inside the case from a mean length of 5 minutes to a mean length of 4 hours. If the device is left unattended, it enters a battery-saving "chirp" mode. Dimensions (inches): 4.15 X .85 X 2.40. Weight including batteries: 4.5 oz. The photos are actual size.
Operating instructions.