A scenario for using these devices safely (
https://www.rfremotech.com/) for personal use would be to have the 12V battery with a relay next to the pad.
A 10 to 25' lead-in wire can go to the receiver a distance away. The relays in most of the receivers are rated 10 amps so there is the potentional of frying them if more current goes through them. Also, do not, do not, do not, do reverse polarity on the receiver units. Do that and POOF! It's gone.
A 30 amp automotive relay coil on one's 12V ignition battery doesn't draw much from those 10 amp traces. I have a surplus solenoid that can switch 200amps on one of my batteries and its coil only draws 2 to 2.5amps on activation. Well within the 10 amp limit of the receiver's rating.
I was able to purchase a 2000 meter transmitter that had 4 DIP switches on the front panel. These are used to set a code for the transmitter which the RR1L
receivers are trained to respond to. I simply scramble the dip switches between use. Even if the on/off switch is "on" no way a launch can take place unless the recessed DIP switches are set to the proper code the receiver's had learned. I've tested it out and it works. If the proper code isn't in, it don't work.
The technique is turn the receiver off. If it's off, it can't respond to anything. Connect up the igniter to the rocket. On the way back to a safe distance to stand, go by and turn on the receiver toggle switch. Get away to the observation position, turn on the transmitter, set the DIP switches to the proper code and ready to fire.
Only problem here is RfRemotech no longer makes this transmitter that I have. I don't know if they have any newer coded devices amenable for rocketry use. Like I said, this is for my own personal use and is not something for switching a bunch of pads. Negates the need for long wire drops. Kurt