Telltale /(?)/

Tell·tale

Telltale

One who officiously communicates information of the private concerns of others; one who tells that which prudence should suppress.
A movable piece of ivory, lead, or other material, connected with the bellows of an organ, that gives notice, by its position, when the wind is exhausted. (Mus.)
A mechanical attachment to the steering wheel, which, in the absence of a tiller, shows the position of the helm. (Naut.)
A machine or contrivance for indicating or recording something, particularly for keeping a check upon employees, as factory hands, watchmen, drivers, check takers, and the like, by revealing to their employers what they have done or omitted. (Mach.)
The tattler. See Tattler. (Zool.)
A thing that serves to disclose something or give information; a hint or indication.
It supplies many useful links and telltales.
— Saintsbury.
An arrangement consisting of long strips, as of rope, wire, or leather, hanging from a bar over railroad tracks, in such a position as to warn freight brakemen of their approach to a low overhead bridge. (Railroads)