Go to the page 20 using Search Inside facility, where the author specifies what a continuity tester should satisfy: "...and be capable of delivering an AC or DC short circuit voltage of not less than 200mA....". Now, any student sitting for an exam of this nature and not knowing the difference between "voltage" and "current" would be thrown out of my classroom. For uninitiated in the electrics or electronics here is a short explanation: The short circuit voltage is by definition 0.V, its resistance is 0.Ohm and the only parameter of interest is current (measured in A or in this case mA) which the instrument can produce in that situation. To have such an error in a textbook in inexcusable, to have it in the 5th edition is criminal. I will leave it to you to conclude if this pathetic attempt of a textbook would help you to learn anything.