Re: Red Button
...and that it (Airwave) offered "peer to peer" facilities (I presume this is what you mean by Gateway operation?) which would be very handy in areas of poor coverage.
Some understandable confusion in there. (Not a criticism, BTW.) "Peer to Peer" is more correctly called Point to Point (P2P) but it still needs the "network" to operate; it enables an individual user to commuicate with another individual user but without involving anyone / everyone else within a Talkgroup. (The downside is that both users become incommunicado from whatever Talkgroup they were previously sitting on.) By definition a Talkgroup operates in Trunk Mode Operation, TMO.
I'll get to "Gateway" via Direct Mode Operation, DMO. DMO can be used between Terminals (a/k/a portable or vehicle radios) in the event of a network failure or in an area of very poor coverage; in this mode they behave very much like conventional radios, and "very much like" includes a significantly reduced range. It is very much a fall - back operation, and would not be anyone's first choice!
Gateway gets complicated. It can be used in areas where network signal strengths are simply not good enough for a portable terminal to function satisfactorily because of its suboptimal aerial* and modest transmitter power, but are good enough for a vehicle radio to operate because of its (hopefully!) better aerial and more powerful transmitter. In this case it is possible to set up a configuration in which the vehicle radio acts as a "repeater" between the network and the portable; the vehicle radio operates primarily in Trunk Mode, with the link between it and the portable terminal operating in Direct Mode. The vehicle terminal thus acts as a Gateway between the portable terminal and the wider network.
I think there was some gnashing of teeth about radios not working properly underground during the Kings Cross fire.
There were a lot of problems, but they did not (would still not) originate from anything mentioned so far. Underground stations are (by definition) underground and poor radio performance in tunnels (which for all practical purposes includes not just the railway tunnels but all the pedestrain passageways and platforms) is a known problem and has been more or less forever. The solution is to install (at considerable cost) "continuous" underground aerials called leaky feeders with either a proper base station at the end of them or a cell enhancer which piggy backs coverage from the nearest serving external cell / base station. The result is that radio users are never more than a few feet from a cable ("aerial") that provides the connection they need. No leaky feeder, no coverage.
Returning briefly to Trunk Mode, Direct Mode, & Gateway, changing between them requires some button pushing and getting it right necessitates remembering what was taught in training. If not done regularly training fade inevitably takes its toll. I've been retired a few years now but getting Gateway right was not straightforward and the outcome not entirely satisfactory; hopefully things have been made easier now, but who knows..?
For the avoidance of doubt; I am not and never have been a Police Officer, but I spent a few years as a civvy in a Police Force working on, er, radio systems both old and new.
* Another thought... I hope Samsung's radios do / will actually have visible external aerials and aren't going to rely on a bit of PCB track inside a shiny case. That takes "suboptimal" to an even lower level. :(