a controlled self - service drink dispensing machine including a refrigerated piping network for transporting beverages , such as wine and beer , from a central location to a plurality of remote dispensing consoles . a centrally located bartender terminal is electronically coupled to each of the remote dispensing consoles which are activated by magnetic credit / debit cards received in the remote consoles . a beverage transparent plastic delivery tube in each remote console is bracketed by a light emitting diode transmitter and receiver system that is electronically coupled to the bartender terminal to alert the bartender of a low keg by sensing the amount of air and / or bubbles flowing through the delivery tube .