The Testboy 114 is a nice toy for detecting voltage at sockets and power cables (cable break detection etc.), as well as covering electrical fields to any electronic devices.
Unfortunately, he acknowledges some switches unclear whether voltage is present or not, and it can not be distinguished clearly L1 and N in some outlets (the device vibrates simply permanently). In fuse boxes no unique assignment is absolutely possible. If I'm working on an electrical outlet, I will continue to rely on my multimeter and not rely on the Testboy.
Cables in walls are usually not recognized correctly because the sensitivity is not yet high enough then.
Furthermore, the device can not be switched off, it is, so to speak always in standby mode.
As described also to install the batteries is quite a hassle ..
Cute as toys and consider the fast if electric fields are present and for the price an absolute bad buy.