UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 4)*

(Name of Issuer)

(Title of Class of Securities)

(CUSIP Number)

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box:  ¨.

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

(Continued on the following pages)

Page 1 of 6 Pages

SCHEDULE 13D

This Amendment No. 4 to Schedule 13D is being filed on behalf of the undersigned as an amendment to the Statement on Schedule 13D filed with the Securities and Exchange Commission on October 12, 2010, as amended by Amendment No. 1 to Schedule 13D filed with the Securities and Exchange Commission on April 2, 2012, Amendment No. 2 to Schedule 13D filed with the Securities and Exchange Commission on April 16, 2012 and Amendment No. 3 to Schedule 13D filed with the Securities and Exchange Commission on May 14, 2012 (as amended, the “Schedule 13D”), relating to shares of Common Stock, par value $0.001 per share (the “Common Stock”), of Dialogic Inc., a Delaware corporation (the “Issuer”). Terms defined in the Schedule 13D are used herein as so defined.

The information in Item 4 is hereby amended and supplemented as follows:

Upon the Stockholder Approval (defined below), the Reporting Person obtained the right to designate four members of the Board of Directors of the Issuer under the terms of the Series D-1 Preferred Stock. Messrs. Nick DeRoma, Dion Joannou, Giovani Richard Piasentin and Rajneesh Vig, who are current members of the Board, have agreed to be Board designees of the Reporting Person.

The information in Item 5 is hereby amended and restated as follows:

On August 8, 2012, the Issuer obtained approval from its stockholders (the “Stockholder Approval”) for (a) the issuance of 18,000,000 shares of Common Stock issuable upon exercise of the Warrants and (b) the Private Placement, which included the sale to accredited investors of $39,529,714.18 aggregate principal amount of the Notes and one share of the Issuer’s Series D-1 Preferred Stock.

Upon obtaining the Stockholder Approval, the Notes automatically converted into an aggregate of 40,103,534 shares of Common Stock. The portion of the Notes held by the Funds converted into 35,453,052 shares of Common Stock. In addition, the exchange cap limiting the exercise of the Warrants to 19.99% of the Common Stock was removed, and the Warrants became exercisable for the full amount of 18,000,000 shares of Common Stock.

(a)-(b) The Reporting Person beneficially owns 55,499,950 shares of Common Stock, which consists of (i) 2,046,898 shares of Common Stock previously held, (ii) 35,453,052 shares of Common Stock issued upon conversion of the Notes and (iii) 18,000,000 shares of Common Stock issuable upon exercise of the Warrants. The 55,499,950 shares of Common Stock beneficially owned by the Reporting Person constitute approximately 61.7% of the outstanding shares of Common Stock of the Issuer, based on (i) 31,850,877 shares of Common Stock outstanding as of June 12, 2012 as reported by the Issuer in its Definitive Proxy Statement filed with the Securities and Exchange Commission on June 27, 2012, (ii) 40,103,429 shares of Common Stock issued upon conversion of the Notes and (iii) 18,000,000 shares of Common Stock issuable upon exercise of the Warrants. The Reporting Person has sole voting and dispositive power over the shares of Common Stock.

(c) Other than the issuance of Common Stock to the Reporting Person upon conversion of the Notes, there have been no transactions in shares of Common Stock effected by the Reporting Person during the past 60 days.

(d)-(e) Not applicable.

SIGNATURE

After reasonable inquiry and to the best of the Reporting Person’s knowledge and belief, the undersigned certifies that the information set forth in this statement is true, complete and correct.

Exhibit Index