This is a helpful hint. I spent 2 hours to figure this out. When sending a fax, my fax machine was not connecting with the other fax machine. I found a button that changed lighted positions when pushed.
The button is next to the start button (Diamond shape). The manual shows that when the button is pushed the light will be on top for color faxes. The light will be on the bottom for black faxes. If the receiver's fax is set to receive black faxes, the receiver's fax will not connect if the light is in the color position for faxes.