Automatic Data Processing Inc. plans to redeem on Nov. 16 its $150 million of 6.5% convertible subordinated debentures due March 1, 2011. 

The computing-services concern will pay $1,059.04 for each $1,000 face amount of debt.
The conversion price for the debentures is $41.725 a share.
In New York Stock Exchange composite trading Friday, Automatic Data closed at $46.50 a share, down $2.25. 

If all the debt is converted to common, Automatic Data will issue about 3.6 million shares; last Monday, the company had nearly 73 million shares outstanding. 

Automatic Data is redeeming the bonds because the after-tax cost of the interest on the bonds is higher than the dividend yield on the common, a spokesman said.