"I see..." So these things have identical Seigels that would make sure that only they would receive each other's signals. Literally like a radio then...
"Wait... If I'm understanding this correctly, both of these devices should be running for them to receive our voices?"
"Correct," Amelie responded to Grigori's question. "Without a constant source of Wesen, the receiver will not be able to intercept the message from the ambient Wesen, essentially rendering the broadcast unheard."
I blinked as a sudden realization hit me. If these things needed to be on at all times, then-
"So we won't know if their device is operational until we hear their voice come out of that box?~" Aria cheerfully teased, unfortunately to the tune of my own thoughts. "That's so bad~"