X0303 4 2010-06-03 0 0001136655 ARBINET Corp ARBX 0001265181 SINGER KAREN 212 VACCARO DRIVE CRESSKILL NJ 07626 0 0 1 0 Common Stock 2010-06-03 4 P 0 143407 1.9398 A 5104447 I As the trustee of the Singer Children's Management Trust The price in Column 4 is a weighted average price. The prices actually paid ranged from $1.9397 to $1.93992980 per share. The reporting person will provide to the Issuer, any security holder of the Issuer, or the SEC staff, upon request, information regarding the number of shares purchased at each price within the range. The reporting person disclaims beneficial ownership of these securities except to the extent of her pecuniary interest therein. This filing shall not be deemed an admission that the reporting person is, for purposes of Section 16 of the Act or otherwise, the beneficial owner of any equity securities covered by this filing. /s/ David J. Hoyt Attorney-in-fact 2010-06-04