If you are a man over 40 encountering mid-life problems, a mother who needs advice on how to feed your child, or just have a problem with cockroaches, Prince George's County can now provide information on these problems and 245 others with its new Tel-Med system.

A "miniature encylopedia" by phone, Tel-Med offers community-oriented information and medical advice on three-to seven-minute tapes. County residents may call a central number and request tapes on such topics as first aid, pregnancy and family planning, arthritis, heart problems, dental care, alcohol and drug abuse, nutrition, cancer and mental health. The tapes also have information on specific concerns of men, women, children and the family.

"It is mostly oriented toward well people," said Robert Martin, vice-president of the Community Services section of the county health office. "I imagine that some people would call Tel-Med before seeing a doctor, but it is not a replacement for a doctor.

"It's a private service," he said. Tapes on male and female sexual response, masturbation, veneral disease and specific birth control methods are available along with information on power lawnmowers, leg cramps and the croup. The most popular tape has been on cockroaches. After a brief history lesson on the origin of the species, it informs the listener that cockroaches may spread such diseases as polio, TB, amoebic dysentery and diarrhea. The only relief from them, it says, is to keep a clean house.

A non-profit system developed by the San Bernadino Medical Society, the Tel-Med system was reviewed, updated and localized by 87 county physicians and dentists in Prince George's. It cost the County Health Department $14,000 with first-year operating expenses coming from the Prince George's County Hospital and Medical Center. The Ladies Guild donated $2,500 for brochures.

Operated by the Prince George's County Library System, Tel-Med has 10 telephone lines and has been receiving over 400 calls a day since it began operation two weeks ago.

Brochures listing all individual tape numbers are available in area businesses, at doctors' and dentists' offices, in libraries and at governmental agencies, or can be obtained by calling 341-3356.

The brochures are mandatory for the system as the caller must request a specific tape number each time he or she calls. No calls can be taken by the operators without a number.

Calls into the Tel-Med number may be made Monday through Thursdays 9 a.m. to 9 p.m., Fridays 9 a.m. to 6 p.m., and Saturdays 9 a.m. to 5 p.m.