Vitamin A deficiency: Related Medical Conditions. To research the causes of Vitamin A deficiency, consider researching the causes of these these diseases that may be similar, or associated with Vitamin A deficiency:
Definition of push button. : a small button or knob that when pushed operates something especially by closing an electric circuit.
The concept of the use of push-buttons in telephony originated around 1887 with a device called the micro-telephone push-button, but it was not an automatic dialing system as understood later. This use even predated the invention of the rotary dial by Almon Brown Strowger in 1891.