Maryland residents will be able to buy certain types of single-line telephone equipment--including what they have in their homes and businesses--from the Chesapeake and Potomac Telephone Co. under an order approved yesterday by the Maryland Public Service Commission.

The equipment sale is the latest local development in the government-ordered reorganization of the telephone company. C&P officials say they will seek regulatory approval within the next several months to sell equipment in Virginia and the District of Columbia.

Under the Maryland plan, C&P will have two sales. One starts today at the C&P service centers in Maryland, which will sell standard, Trimline and Princess telephones out of telephone company inventory for prices ranging from $34.95 to $74.95.

The second sale starts Feb. 1 and will consist of single-line standard, Trimline and Princess phones in place in customer homes and businesses as of midnight last night. Customers who buy their home and business equipment during the special 90-day introductory offer beginning Feb. 1 will pay $15 to $20 less than the phone service center prices.

C&P customers who prefer to continue leasing their equipment will be able to do so.

"Bill inserts explaining the special sale will go out to customers in their February statements," said C&P representative Web Chamberlin. Customers have 90 days from the date of their February bill to buy at the reduced price. After the 90 days, in-home equipment will cost the same as equipment for sale in the phone stores.

C&P will provide a 90-day warranty covering repair or replacement of telephones sold from inventory. The warranty on equipment sold that is already in place on customer premises will be for 30 days.

The least expensive telephone is the standard rotary desk and wall set, which will sell for $34.95 at the C&P service centers in Maryland. During the introductory sale, a Maryland customer with that telephone now in use will pay $19.95. Maryland residents now pay $1.15 a month to lease that set.