After a few attempts the design below was drawn up, a higher resolution copy can be downloaded from the bottom of this page.
The circuit is labelled up ready for the development of an alarm system, however the available I/O could be reused to suit many applications.
This is most likely not the final version as deficiencies can already be seen in the design
but these shall be addressed later when the design is revisited.
However for now this will provide a reasonable starting point to allow development to continue.
The design was transferred onto strip board for construction:
This is the core undergoing testing.