Radio Woes

[Marcus Merritt]

1994; 4.9L; Automatic; 117k miles. Took the battery out recently to put in new horn and now the stock radio has a message that is: 'Tape (what looks like an asterisk and then the 'tape' letters). I cannot get rid of this message and I do not have a tape deck in the truck. Just AM and FM. In the past, when listening to an FM station the 'Tape message would flash and interrupt the FM reception. Note that this 'Tape message shows up whenever I've disconnected the battery in the past but seems to disappear over time and the radio will operate normally. What is this signal and how can I get my radio back?? Does anyone know where I can get a radio manual? My truck manual refers to one but I do not have it. Thanks.