1) Music venue in Los Angeles 
The Echoplex is a tape delay effect, first made in 1959. Designed by Mike Battle, the Echoplex set a standard for the effect in the 1960s—it is still regarded as `the standard by which everything else is measured.` It was used by some of the most notable guitar players of the era; original Echoplexes are highly sought after. ==The original tub.....
a method of loop checking by which each transmitted character is displayed in-local after its return from the distant station
Mode in which keyboard characters are echoed on a terminal screen upon return of a signal from the other end of the line indicating that the characters were received correctly.