I bought a Flextone model ER1 electronic call this week. It has 100 preloaded game calls. You can choose between one or two speakers & can use it out to 300 yds. I set up about 150 yds away Saturday morning & things worked as they should. I didn't take the time to try any further away, as the wind was really blowing and I didn't know if I could hear it much farther away.
I called in two large coyotes right as the sun was coming up, but didn't get a shot. They were running along together & didn't slow down much.
I did waste a skunk though.