UNC Inc., an Annapolis-based technology and services company, has adopted a new "poison pill" antitakeover measure that would give its stockholders the ability to buy stock at a discount in an unwanted acquirer's company.

The plan toughens the company's previous poison pill provision and is similar to plans adopted in recent months by other local companies.

It will give UNC shareholders "share purchase rights" enabling them to buy 1/100 of a share of a new series of preferred stock for $50. The plan would only go into effect if a person or group buys 20 percent or more of UNC's stock or announces a tender offer for 20 percent or more of the company's stock.

Under the plan, UNC shareholders then could purchase $100 worth of the acquiring company's stock for $50 for each of the "share purchase rights" they own.

In addition, stockholders would be able to acquire $100 worth of UNC common stock for $50 for each right.

The acquiring company would be excluded from the plan.

The plan could be deactivated by the UNC board to allow a friendly takeover of the company.

The company said it put the plan into place to "ensure that all of UNC's stockhold- ers receive fair and equal treatment in the event of any proposed takeover of the company and to guard against partial tender offers and other abusive tactics to gain control of UNC."

"The issuance of the new rights reflects our continuing review of the problem of takeover abuses and our effort to provide our stockholders with the best available protections," Dan A. Colussy, UNC's president, said in a statement.