Learning electronics in theory by studying books is the conventional way, this method may help in History and Maths. Maths needs a paper and pencil for practicals and history needs a well equipped Library. In these modern times, the web has made access to wide range of learning information easy, which is true Knowledge Empowerment. The greatest gift a Child can get from the Parents or School, is Knowledge.
Solid State Relays - These designs were improvements i made on the Application Notes of Motorola Semiconductor (freescale) and Thomson CSF (stmicro) Thyristor Data. The parts are still available, now made by other firms. You can also find similar equivalents.
Digital Interface to Analog Circuits is an example of Mixed Signal Design. Generating Digital Control Signals from the Analog sections in instruments is also done by Mixed Signal Circuit.
A/D Convertors and D/A Convertors are like Mixed Signal Chips. A Digital Potentiometer that controls an analog signal amplitude with a digital byte or word, figures in Mixed Design Circuit.
Temperature Controller 48-96 - A 1/8 DIN Indicating Temperature Controller. This is a Analog Controller built around ICL7107. This is a 48-96 DIN Temperature Controller, it is mains operated, it is in a Industrial Plastic Housing. It is not meant for very harsh environments.
Control panels are a part of industrial automation. It contains many DIN standard instruments both in the front panel and inside back rails along with the wiring. They are called panel mounting and rail mounting. Cable management is a Science in these equipment.