Abstract: A machine requiring periodic maintenance, such as a vending machine, is retrofitted to include an alert system for notifying a machine operator that the machine requires servicing. The alert system includes one or more sensors to detect default conditions, a voice recorder for storing one or more voice messages corresponding to default conditions, a transmitter for transmitting the voice messages to the machine operator, and a trigger connected to the one or more sensors and the transmitter for selectively initiating the transmission of appropriate voice messages in accordance with predetermined parameters. The voice messages are transmitted over the public switched telephone network (PSTN) to be heard by the machine operator or stored on the machine operator's voice answering system. The transmitter may be a simple auto dialer connected by wires to a nearby phone jack.