Communication With Another World

"...he gripped a small crucifix that hung about his neck, symbol and source of help from beyond this world."
-Poul Anderson, "Death and the Knight" IN Anderson, Time Patrol (Riverdale, NY, 2010), pp. 737-765 AT p. 746.

The crucifix is not only a symbol but also a source of help because it is a Time Patrol communicator.

"'You've been seen muttering at them, not in any way a man would pray to a saint. What were you invoking?'"
-Poul Anderson, The Shield Of Time (New York, 1991), 1245beta, p. 409.

Invoking fellow Patrol agents.

"...he could still reach the communicator hung around his neck. Doubtless a superstitious unease had saved it from being taken off him. Once again he pressed the button. 'Mark,' he whispered. 'Anyone. I am in need.' There was still no answer."
-Poul Anderson, Three Worlds To Conquer (London, 1966), Chapter 9, p. 63.

But Mark exists and is a human being on a moon.