Transcribed from an email:

How do I understand the Signal Strength field returned by the PNPC01 Concentrator

As per normal OpenHAB2 convention, signal strength is a value between 0 and 4, where 0 is no signal and 4 is perfect signal.

Of course, the normal Receiver Signal Strength Indication (RSSI) scale is -100 to 0 dBm, where -100 is bad signal, and 0 is perfect. We first convert from the friendcom scale to that scale, and then from there to the 0 to 4 scale used by the default OpenHAB visual signal control.

You can of course customize your Concentrator as per normal OpenHAB2 procedures to show the UI you want, together with all the fancy controls and dials, that is why we use the scale most suited to the OpenHAB signal indicator. But that is more for the budding open source enthusiasts amongst you, since you'll probably have to edit some OpenHAB related ASCII files on the operating system file system. :-)