Again, citations from hydra.umn.edu/derrida/diff.html
“…So much so that the detours, locudons, and syntax in which I will often have to take recourse will resemble those of negative theology, occasionally even to the point of being indistinguishable from negative theology. Already we have had to delineate that différance is not, does not exist, is not a present-being (on) in any form; and we will be led to delineate also everything that it is not, that is, everything; and consequently that it has neither existence nor essence. It derives from no category of being, whether present or absent. And yet those aspects of différance which are thereby delineated are not theological, not even in the order of the most negative of negative theologies, which are always:': concerned with disengaging a superessentiality beyond the finite categories of essence and existence, that is, of presence, and always hastening to recall that God is refused the predicate of existence, only in order to acknowledge his superior, inconceivable, and ineffable mode of being.”
As such différance is on the fringe, neither something external to language, affecting it from without, prior to it nor something inscribed within language, present in language at any time. This metaphor of the fringe (also the supplement, the hymen, the membrane, the spectre and so on) occurs throughout Derrida’s work and demonstrates above all his concern at the limits of phenomenological language and those things sit on the cusp of the dualism of the inner and the outer, another recurring metaphor on which logocentrism (western metaphysics, the metaphysics of presence) frequently rests.
“For the same reason there is nowhere to begin to trace the sheaf or the graphics of différance. For what is put into question is precisely the quest for a rightful beginning, an absolute point of departure, a principal responsibility…In the delineation of différance everything is strategic and adventurous. Strategic because no transcendent truth present outside the field of writing can govern theologically the totality of the field. Adventurous because this strategy is not a simple strategy in the sense that strategy orients tactics according to a final goal, a telos or theme of domination, a mastery and ultimate reappropriation of the development of the field. Finally, a strategy without finality.”
Expressed in terms of systems (and if one accepts the inclusion of dynamic structures under the banner 'systems) the argument is elucidated by McQuillan, "Consider the following universal system:

Imagine a system in which all the systems of the world (A to Z) are related. In order for this system to be a system (for it to be systematic) it must be closed. A to Z must be related in clear and predictable ways in order to their relation to be systematic and this means that there must be a discernible limit to the action of the system. So, let us call this system of systems the universal system and its aim is to relatve all known systems to one another. There are two consequences from this description. First, if there is indeed a limit to the action of the system then something must exist outside the system. Whenever we draw a limit we are defining what is inside the limit by presupposing an outside the limit. Thus if there is something outside the limit of the universal system then system cannot be universal because it leaves something unaccounted for. Secondly, what is it that the universal system does not account for? Which system lies outside the closed field of systematic relations described by the ‘universal system’? The answer is the universal system itself. The universal system cannot account for itself as a system. To do so would be to recognise that impossibility of maintaining the limit to the universal system and so to admit that it is neither systematic nor universal. In this way the universal system, far from regulating all systems, would have to admit that no system can be truly systematic because it is not possible to maintain the rigorous purity of a limit. The universal system demonstrates the impossibility of the system per se, and so undoes the logic of a ‘properly’ maintained inside and outside." (Mcquillan, 5 strategies for deconstruction, 2000)
Derrida curiously admits the possibility of différance being one day seen as simply part of a theoretical progression and tradition, of it one day surrendering its fringe status and being established, contextualised, firmly within language, “Also, by decision and as a rule of the game, if you will, turning these propositions back on themselves, we will be introduced to the thought of différance by the theme of strategy or the stratagem. By means of this solely strategic justification, I wish to underline that the efficacity of the thematic of différance may very well, indeed must, one day be superseded, lending itself not only to its own replacement, at least to enmeshing itself in a chain that in truth it never will have governed. Whereby, once again,it is not theological.” I’m not sure whether this is false modesty, Derrida covering his own ass, scepticism towards the claims of radicalism made by such a philosophy or a genuine confession. Nonetheless it remains a point oft overlooked by those who seek to criticise Derrida, not to mention those who worship him uncritically.
Rather typically, Derrida goes on to offer a brief semantic analysis of a word which is designed to threaten the very possibility of such an analysis and resists it at every turn. This is a prime example of Derrida failing, but his failure simply re-affirms his conclusion.
“We know that the verb differer (Lahn verb differre) has two meanings which seem quite distinct; for example in Littré they are the object of two separate articles. In this sense the Latin differre is not simply a translation of the Greek diapherein, and this will not be without consequences for us, linking our discourse to a particular language, and to a language that passes as less philosophical, less originally philosophical than the other. For the distribution of meaning in the Greek diapherein does not comport one of the two motifs of the Latin differre, to wit, the action of putting off until later, of taking into account, of taking account of time and of the forces of an operation that implies an economical calculation, a detour, a delay, a relay, a reserve, a representaton - concepts that I would summarize here in a word I have never used but that could be inscribed in this chain: temporization. Differer in this sense is to temporize, to take recourse consciously or unconsclously, in the temporal and temporizing mediation of a detour that suspends the accomplishment nor fulfillment of “desire” or “will,” and equally effects this suspension in a mode that annuls or tempers its own effect. And we will see, later how this temporization is also temporalization and the becoming-time of space and the becoming-space of time, the “originary constitution” of time and space, as metaphysics or transcendental phenomenology would say, to use the language that here is criticized and displaced.”
I’ll leave the phenomenology for James No. 2 to discuss if he feels like it as I think that he’s probably better informed than I am. But here we see the entwining, the ensheafing of space and time together, of difference (spatialisation) and deferance (temporisation) and how for Derrida the two are tied together, if not logically or phenomenologically then for anyone attempting an analysis of language.
Next we get into one of the main targets of Derrida’s philosophy - the notion of the sign as secondary (one of a series of presumptuous prejudices Derrida attacks throughout his works, and one made by detrop on this very thread):
“Let us start, since we are already there, from the problematic of the sign and of writing. The sign is usually said to be put in the place of the thing itself, the present thing, “thing” here standing equally for meaning or referent. The sign represents the present in its absence. It takes the place of the present. When we cannot grasp or show the thing, state the present, the being-present, when the present cannot be presented, we signify, we go through the detour of the sign. We take or give signs. We signal. The sign, in this sense, is deferred presence. Whether we are concerned with the verbal or the written sign, with the monetary sign, or with electoral delegation and political representation, the circulation of signs defers the moment in which we can encounter the thing itself make it ours, consume or expend it, touch it, see it, intuit its presence. What I am describing here in order to define it is the classically determined structure of the sign in all the banality of its characteristics - signification as the différance of temporization. And this structure presupposes that the sign, which defers presence, is conceivable only on the basis of the presence that it defers and moving toward the deferred presence that it aims to reappropriate. According to this classical semiology, the substitution of the sign for the thing itself is both secondary and provisional: secondary due to an original and lost presence from which the sign thus derives; provisional as concerns this final and missing presence toward which the sign in this sense is a movement of mediation.”
Here, I hope, we see the connection between language, general semiology and the metaphysics of presence which are being called into question. This association occurs in much of Derrida’s work but I’ve not ffound a passage which is more clear in its descriptions than this one.
…
"In attempting to put into question these traits of the provisional secondariness of the substitute, one would come to see something like an originary différance; but one could no longer call it originary or final in the extent to which the values of origin, archi-, telos, eskhaton, etc. have always denoted presence - ousia, parousia. To put into question the secondary and provisional characteristics of the sign, to oppose to them an “originary” différance, therefore would have two consequences.
- One could no longer include différance in the concept of the sign, which always has meant the representation of a presence, and has been constituted in a system (thought or language) governed by and moving toward presence."
Such ‘moving toward’ would be immeasureable because one is using language (defered presence) to analyse and measured the extent to which which presence is deferred (a similar paradox to that of the universal system explained above).
“2. And thereby one puts into question the authority of presence, or of its simple symmetrical opposite, absence or lack. Thus one questions the limit which has always constrained us, which still constrains us - as inhabitants of a language and a system of thought - to formulate the meaning of Being in general as presence or absence, in the categories of being or beingness.”
Hence Derrida’s use of such metaphors as I mentioned earlier…