Non-standard capability, e.g. relay, mail-box

Full Title

Indexing scheme relating to scanning, transmission or reproduction of documents or the like, and to details thereof > Circuits or arrangements for control or supervision between transmitter and receiver or between image input and image output device, e.g. between a still-image camera and its memory or between a still-image camera and a printer device > Mode signalling or mode changing; Handshaking therefor > of a particular mode > Non-standard capability, e.g. relay, mail-box