Hi Harry - A premicell unit is basically a mobile telephone in a box that acts as a gateway between a mobile network and a wired network such as your ordinary home phone. Some companies attach them to a switchboard so users can call a mobile on the same network (usually their own staffs) at a cheaper rate.
You locate the box wherever suitable and wire in landline telephones. In the mountain rescue communications vehicle I wired two ordinary household telephones - one in the front of the vehicle accesible to the driver and one in the rear where search management and communications would happen. I used ordinary household telephone cable and sockets. This gives me two phones either of which can be used to make/answer a call. I have a spare socket into which a fax machine or modem can be connected. An external aerial is fitted to the outside of the vehicle. In extreme locations the aerial can also be routed up a pump up mast (a bit extreme for a motorhome, although some locations in Scotland I could see the benefit!!) extending the range.
The units are intended for use in remote location houses where a landline may not be an option. Like a mobile phone they normally work from a mains powered small transformer, a bit like the charger for an ordinary mobile. I simply sourced a 12 volt converter that would drop the vehicle supply to the 6 volts the unit I had needed and hard wired that into the supply through a suitable isolating switch and
fuse. This allows it to be switched off if not needed.
The Premicells should be Sim free and all you do is slot in your own Sim however make sure the Premicell supports the band(s) you want to access while mobile (GSM900, GSM1800 for UK/Europe, G3 etc).
I can not comment on the 3G aspect as I have not used it for that, however I see no reason why it should not make an improvement overall. One of the problems with handheld units is that they have small aerials internally and users hold them at odd angles and even holding them drops the signal strength some.
these factors will contribute to weak signals, weak signals introduce errors which the system compensates for by requesting the same information again and again until it is successfully received. All of this redundancy leads to slow delivery of data which a premicell unit may overcome. Hope this helps.
Robert
