Commissioner Gordon's phone

The red phone in Gotham City Police Headquarters was kept under a transparent protective dome in the office of Police Commissioner James Gordon.
When Batman's help was needed, the cover was removed, the handset was lifted and a button in the phone's center was pressed. At this point the phone would start to flash and beep as if a call was coming in, like the phone in Wayne Mansion.
These audio-visual efects were unrealistic and unnecessary, but were certainly dramatic.
(Photos from the ABC TV series)