I am actually using this book. I am selling it because I passed the exam. Post-it notes are attached to the parts I thought were important to memorize. There is also some writing in it, about a few percent of the whole book. Please understand that this is a used item before purchasing. A practical reference book that explains the exam questions from the past five times. - Title: 1st Class Digital Communication Practical Problems 2023 Edition - Contents: Easy-to-understand explanations of the exam questions from the past five times. Thank you for looking.