The French terms of both agencement and dispositif used by Deleuze and Guattari are usually translated as assemblage. An assemblage is a "site at which a discursive formation intersects with material practices" (Jonathan Crary, Techniques of the Observor, p. 31) It is "simultaneously a machinic assemblage and an assemblage of enunciation" (D+G, Thousand Plateaus, p. 504)

"Concepts are concrete assemblages, like the configurations of a machine, but the plane of immanence is the abstract machine of which these assemblages are the working parts." (What is Philosophy?, p.36) Assemblages are passional, they are compositions of desire . There is no desire but assembling, assembled desire. (according to Brian Massumi, Deleuze and Guattari substituted the term assemblage for the term desiring machine because of persistent subjectivist misunderstandings of the latter term as developed in the Anti-Oedipus.)

Machines are social before being technical" (Deleuze, Foucault, p.39) Deleuze goes on to say, that for Foucault, at least, "there is a human technology which exists before a material technology." "...And if techniques -- in the narrow sense of the word -- are caught within the assemblages, this is because the assemblages themselves, with their techniques, are selected by the diagrams." ....For a material technology to be even possible, "the tools or material machines have to be chosen first of all by a diagram and taken up by assemblages. Historians have often been confronted by this requirement: the so-called hoplite armies are part of the phalanx assemblage; the stirrup is selected by the diagram of feudalism; (cf. Lynn White Medieval Technology and Social Change ) (see warthe burrowing stick, the hoe, and the plow do not form a linear progression but refer respectively to collective machines which vary with the density of the population and the time of the fallow...Technology is therefore social before it is technical." 

..."a technical element remains abstract, entirely undetermined, as long as one does not relate it to an assemblage it presupposes. It is the machine that is primary in relation to the technical element: not the technical machine, itself a collection of elements, but the social or collective machine, the machinic assemblage that determines what is a technical element at a given moment, what is its usage, extension, comprehension, etc.It is through the intermediary of assemblages that the phylum selects, qualifies, and even invents the technical elements. " (Thousand Plateaus, pp397-8) 

Hardt and Negri's gloss on Deleuze's reading of Foucault (!) describe the dispositif and the diagram as a series of abstractions. (Empire, pp 329-330) "In somewhat simplified terms, we can say that the dispositif (which is translated as either mechanism, apparatus, or deployment) is the general strategy that stands behind the immanent and actual excercise of discipline. At a second level of abstraction, the diagram (or virtual design ) enables the deployments of the disciplinary dispositif.