Device for the jacket pocket with high reliability

The device is small as a cell phone, so unobtrusive when it is in the jacket. Built telescopic mouthpiece is a plus. Batteries last long enough for occasional use (1x party use / month). Has a high fun factor. However, the menu navigation via dial operation is only easy if you work more than 1x / month with the device, because the handling quickly forgotten and for the occasional longer calibration time (10-30 sec) can often cast doubt on the intuitive operation. In the case then I do like other devices, if I have no more patience for a feedback of the device, attempt to turn the power off / on, which does not by a simple push of a button works, but on more seconds pressure and reaffirmation. If you have previously read on the display values ​​such as 1.0 parts per thousand, is sometimes no longer sooooooo easy to use. But the battery compartment just goes on and ;-).
Unfortunatley my device already 5 of 24 months, with new factory calibration is required on the clock, even though it was a new purchase. For a point deduction. All in all, I would buy the device again.