This read-only object indicates whether a given interpreter is capable of sending information back to the host over a backchannel, rather than only accepting incoming print data. An admin relies on this to know whether bidirectional features like status queries or job feedback are even possible for jobs processed by that interpreter. For example, an interpreter reporting ePno(4) tells the admin not to expect any backchannel status updates for jobs sent through it, ruling that out when a driver's status polling silently fails.