One of a handful of TZ episodes that, notably, contains no science fiction or fantasy elements. Others include Dust (1961), The Shelter (1961), and The Silence (1961).
The tape recorder seen is a Selectron International model TP-411 manufactured by Aiwa.
Three years later, John van Dreelen would guest star with series regular Martin Landau in the episode of Mission: Impossible (1966) titled The Diamond (1967).
Martin Landau (Major Ivan Kuchenko) later played William Cooper-Janes in The Beacon/One Life, Furnished in Early Poverty (1985).