Long time ago, I made a "Mastermind" box for 4 contestants with cables and pushbuttons for my kids to play "pub quiz" type games. You ask a question, and first on the button locks the others out and gets to answer the question. The kids now have their own kids and it still gets used at Christmas. But my now 42 y.o. daughter said a couple of months ago "it would be great if the mastermind box were cordless.. hows about it Dad?" So I made an IR version using TV handsets and that was not quite good enough.. the serial transmission was a bit too slow if 4 people were pressing at the same time, and also they complained it was directional; they had to "aim" the handsets at the box (how awful?). Hence the change to 4 x 8T4 fobs and ZPT receiver. This works very well. The serial packet is long but goes fast (19.2Kbaud, I believe) so "lock out", by pressing 2 fobs at exactly the same time, is very rare and can still be recovered by letting your button go and quickly pressing a second time. I did have to use a receiver ariel. I used 6" of solid wire, which I think is roughly half a wavelength. Without it, the range was poor (about 4 metres). With this ariel it worked at 50 metres, and would probably do more but I could not hear or see the box any more at more than 50m (eyes and ears getting a bit feeble). For interest, the power supply arrangement was Ideal. For the display, I used LED strips, 6 LEDs per segment making a large 7-segment display displaying 1-4. I used a beeper to give 1-4 beeps too. The brainy bit was an Arduino Nano. So, the large home-made 7-segment display ran on 9V from a rechargeable PP3 battery (it is plenty bright at 9V). The Arduino Nano also works fine on 9V, and the Nano, as well as having its own +5V regulator, gives out a 3.3V supply with more than enough current for the ZPT receiver. I can confirm that the (5V) Nano faultlessly reads the 3.3V signals from the ZPT receiver without tieups, and of course I "taught" the receiver to read only one button from each fob (to avoid tactical cheating) - you probably wouldn't believe how competitive 40-50 y.o. "kids" are! So, a big thumbs up from me on all accounts except for one small thing. I was "forced" to pay for super-fabby fast delivery at a crazy price for a small parcel, for which I could have happily waited a week. But technically, an excellent solution to a request I couldn't refuse (pride was at stake here). Thank you, RF Solutions for helping an OAP to find the answer.