195770
The kraakdoos is a simple device , based around a single operational amplifier ( one of the earliest models to be produced ) and a few transistors , and can be easily constructed by someone with a basic understanding of electronics .
 None
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 None