AEDP-7085 provides interoperability standards for three classes of data links used for transmission of ISR data Point-to-point digital ISR data links, broadcast digital ISR data links, and analogue ISR data links. Throughout this document a data link used to carry commands and associated data to a sensor and sensor platform is referred to as a forward link, and a link used to carry sensor data is referred to as a return link. Some realisations may use only a return link (simplex operation); others may use both forward and return links (duplex operation). Simplex operation may be a fallback arrangement for systems normally employing duplex operation. Relays may be used to extend the operational range of the data link.