Note
Allied Radio catalog 1954 (copyright 1953), p. 48.
QST, Jan 1954, p. 83.
QST, May 1955, p. 84. (a few details)
Allied Radio catalog 1956 (copyright 1955), p. 197.
Walter Ashe catalog 1957 (probably issued in 1956), p. 4.
Allied Radio catalog 1958 (copyright 1957), p. 269.
Allied Radio catalog 1960 (copyright 1959), p. 402.
Allied Radio catalog 1961 (copyright 1960), p. 398..
Allied Radio catalog 1962 (copyright 1961), p. 279.
The Signal Sentry served several station functions. It worked as an RF-actuated CW monitor with adjustable tone and volume. A front-panel switch turned it into a phone monitor to check on-the-air signal quality. It provided break-in muting for the station receiver, and with slight modification could be used as a code practice oscillator. The unit used two tubes and required an external power source.