ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission (SEC) using a "shelf" registration process. Under this shelf registration process, we may offer from time to time, in one or more offerings, a maximum of 750,000 shares that may be issued separately, an indeterminate number of warrants to purchase up to a maximum of 750,000 shares, and up to a maximum of 750,000 shares underlying such warrants. Each time we offer securities, we will provide you with a prospectus supplement that describes the specific amounts, prices and terms of the securities we offer. The prospectus supplement also may add, update or change information contained in this prospectus. You should read carefully both this prospectus and any prospectus supplement together with additional information described below under the caption "Where You Can Find More Information."

This prospectus does not contain all the information provided in the registration statement we filed with the SEC. For further information about us or our securities offered hereby, you should refer to that registration statement, which you can obtain from the SEC as described below under the heading "Where You Can Find More Information."

You should assume the information appearing in this prospectus is accurate only as of the date on the front cover of this prospectus. Our business, financial condition, results of operations and prospects may have changed since that date. We have summarized certain documents and other information in a manner we believe to be accurate, but we refer you to the actual documents for a more complete understanding of what we discuss in this prospectus.

You should rely only upon the information contained or referred to in this prospectus, any prospectus supplement and the registration statement of which this prospectus is a part. We have not authorized any other person to provide you with different information. If anyone provides you with different or inconsistent information, you should not rely on it.

Before making an investment decision, you should carefully consider the risks described under "Risk Factors" in the applicable prospectus supplement and in our most recent Annual Report on Form 10-K, and in any updates to those Risk Factors in our Quarterly Reports on Form 10-Q, together with all of the other information appearing in this prospectus or incorporated by reference into this prospectus and any applicable prospectus supplement, in light of your particular investment objectives and financial circumstances. Our business, financial condition or results of operations could be materially adversely affected by any of these risks. The trading price of our securities could decline due to any of these risks, and you may lose all or part of your investment.

We design, produce, market, sell, and support broadband and dial-up modems, Voice over Internet Protocol or "VoIP" products and services, Bluetooth wireless products, and other communication-related products. Our primary objective is to build upon our position as a leading producer of Internet access devices, and to take advantage of a number of trends in communications including enhanced Internet access, higher data rates, and voice calls traveling over the Internet.

Dial-up modems were Zoom's highest revenue category for many years. Generally our sales of dial-up modems have been declining and other product categories have become increasingly important.

Our dial-up modems connect personal computers and other devices to the local telephone line for transmission of data, fax, voice, and images. Our dial-up modems enable personal computers and other devices to connect to other computers and networks, including the Internet and local area networks, at top data speeds up to 56,000 bits per second.

In response to increased demand for faster connection speeds, we have expanded our product line to include DSL modems, cable modems, and related broadband access products. Our Asymmetric Digital Subscriber Line modems, known as ADSL modems or DSL modems, provide a high-bandwidth connection to the Internet through a telephone line that typically connects to compatible DSL equipment in or near the central telephone office. Zoom is shipping a broad line of DSL modems. Some are fairly basic, designed to connect to the USB port of a Windows computer or the Ethernet port of a computer, router, or other device. Other Zoom DSL modems are more complex, and may include a router, a four-port switch, a firewall, a wireless access point, and other enhanced features. For a given DSL hardware platform, we often provide model variations with a different power supply, filters, firmware, packaging, or other customer-specific items.

Cable modems provide a high-bandwidth connection to the Internet through a cable-TV cable that connects to compatible equipment that is typically at or near the cable service provider. We began shipping cable modems during 2000. Our cable modem customers in the U.S. and other countries are primarily focused on the retail sector.

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We are currently shipping VoIP products which enable broadband users to make phone calls through the Internet, potentially lowering the cost of the call and providing other benefits such as the ability to manage and track calls using a Web browser. 2005 shipments included a multi-function DSL gateway with VoIP, and we also shipped a router with VoIP for use with either a DSL modem or cable modem. In February 2006 we began shipping the first products in a line of analog telephone adapters (ATAs), which connect to a router and one or more phones, and provide VoIP capabilities to the connected phones.

Some of our VoIP products are targeted for sale to service providers, and some others are targeted for sale through our sales channels to end-users. Some of Zoom's VoIP products benefit from Zoom's Global VillageT VoIP service. Global Village's VoIP service enables an end-user to make free VoIP phone calls to end-users of several VoIP service providers, including Global Village, and also allows a user to pay to call almost any phone in the world. Zoom also has a private-label VoIP service called VoIP ASAP, which enables a service provider to offer VoIP service using that service provider's name and logo.

Zoom's product line includes wireless products, including wireless-G network products and Bluetoothr products.

We are incorporated in Delaware under the name Zoom Technologies, Inc. We conduct our business through our operating subsidiary, Zoom Telephonics, Inc. Zoom Telephonics, Inc., was originally incorporated in New York in 1977 and changed its state of incorporation to Delaware in 1993. Our principal executive offices are located at 207 South Street, Boston, MA 02111 and our telephone number is (617) 423-1072. Our web site address is www.zoom.com . Information on our web site is not part of this prospectus.

Some of the information in this prospectus, any prospectus supplement, and the documents we incorporate by reference contains forward-looking statements within the meaning of the federal securities laws. You should not rely on forward-looking statements in this prospectus, any prospectus supplement, and the documents we incorporate by reference. Forward-looking statements typically are identified by use of terms such as "anticipate," "believe," "plan," "expect," "future," "intend," "may," "will," "should," "estimate," "predict," "potential," "continue," and similar words, although some forward-looking statements are expressed differently. This prospectus, any prospectus supplement, and the documents we incorporate by reference may also contain forward- looking statements attributed to third parties relating to their estimates regarding the growth of our markets. All forward-looking statements address matters that involve risk and uncertainties, and there are many important risks, uncertainties and other factors that could cause our actual results, as well as those of the markets we serve, levels of activity, performance, achievements and prospects, to differ materially from the forward-looking statements contained in this prospectus, any prospectus supplement, and the documents we incorporate by reference.

You should also consider carefully the statements under "Risk Factors" and other sections of this prospectus, any prospectus supplement, and the documents we incorporate by reference, which address additional facts that could cause our actual results to differ from those set forth in the forward-looking statements. We caution investors not to place significant reliance on the forward-looking statements contained in this prospectus, any prospectus supplement, and the documents we incorporate by reference. Except as required by law, we undertake no obligation to publicly update or review any forward-looking statements, whether as a result of new information, future developments or otherwise.

Except as otherwise provided in a prospectus supplement, we will use the net proceeds from the sale of the securities covered by this prospectus for general corporate purposes. When a particular series of securities is offered, the prospectus supplement relating to that offering will set forth our intended use of the net proceeds received from the sale of those securities.

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DESCRIPTION OF COMMON STOCK

The following description summarizes the material terms and provisions of our common stock. The following summary description of our common stock is based on the provisions of our Certificate of Incorporation and Bylaws, which are incorporated herein by reference and the applicable provisions of Delaware General Corporation Law. This information is only a summary and is qualified in its entirety by reference to our Certificate of Incorporation and Bylaws and the applicable provisions of Delaware General Corporation Law.

We are authorized to issue 25,000,000 shares of common stock. As of January 16, 2009, there were outstanding:

• 1,871,058 shares of common stock outstanding;
• 288,700 shares issuable upon the exercise of options issued pursuant to our current stock option plans; and
• 755,189 shares issuable upon the exercise of options available for future grant under our stock option plans.

The holders of our common stock are entitled to receive dividends out of legally available assets at such times and in such amounts as our Board of Directors may from time to time determine. Each stockholder is entitled to one vote for each share of common stock held on all matters submitted to a vote of stockholders. Cumulative voting for the election of directors is not authorized.

Our common stock is not subject to conversion or redemption and holders of our common stock are not entitled to preemptive rights. Upon the liquidation, dissolution or winding up of our company, the remaining assets legally available for distribution to stockholders, after payment of claims or creditors, are distributable ratably among the holders of our common stock outstanding at that time. Each outstanding share of common stock is fully paid and nonassessable.

Provisions of Delaware law and our Certificate of Incorporation, as amended, and Bylaws could make the acquisition of our company through a tender offer, a proxy contest or other means more difficult and could make the removal of incumbent officers and directors more difficult. We expect these provisions to discourage coercive takeover practices and inadequate takeover bids and to encourage persons seeking to acquire control of our company to first negotiate with our Board of Directors. We believe that the benefits provided by our ability to negotiate with the proponent of an unfriendly or unsolicited proposal outweigh the disadvantages of discouraging these proposals. We believe the negotiation of an unfriendly or unsolicited proposal could result in an improvement of its terms.

Our Bylaws do not permit stockholders to call a special meeting of stockholders. Our Bylaws provide that special meetings of the stockholders may be called only by a majority of the members of our Board of Directors or our President. Our Bylaws require that all stockholder actions be taken by a vote of the stockholders at an annual or special meeting, and do not permit our stockholders to act by written consent without a meeting. Our Bylaws provide for an advance notice procedure for stockholder proposed nominations of persons for election to the Board of Directors. At an annual meeting, stockholders may only consider nominations specified in the notice of meeting or brought before the meeting by or at the direction of the Board of Directors. Our Bylaws may have the effect of precluding the conduct of business at a meeting if the proper procedures are not followed. These provisions may also discourage or deter a potential acquirer from conducting a solicitation of proxies to elect the acquirer's own slate of directors or otherwise attempting to obtain control of our company.

Our common stock is listed on the NASDAQ Capital Market under the symbol "ZOOM.".

The transfer agent for our common stock is Computershare located at 1745 Gardena Avenue, Glendale CA 91204.

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DESCRIPTION OF WARRANTS

The following description, together with the additional information we may include in any applicable prospectus supplements, summarizes the material terms and provisions of the warrants that we may offer under this prospectus and the related warrant agreements and warrant certificates. While the terms summarized below will apply generally to any warrants that we may offer, we will describe the particular terms of any series of warrants in more detail in the applicable prospectus supplement. If we so indicate in the prospectus supplement, the terms of any warrants offered under that prospectus supplement may differ from the terms described below. Specific warrant agreements will contain additional important terms and provisions and will be incorporated by reference as an exhibit to the registration statement which includes this prospectus.

We may issue warrants for the purchase of common stock in one or more series. We may issue warrants independently or together with common stock, and the warrants may be attached to or separate from the common stock.

We will evidence each series of warrants by warrant certificates that we may issue under a separate agreement. We may enter into the warrant agreement with a warrant agent. We will indicate the name and address of any such warrant agent in the applicable prospectus supplement relating to a particular series of warrants.

We will describe in the applicable prospectus supplement the terms of the series of warrants, including:

• the offering price and aggregate number of warrants offered;
• the currency for which the warrants may be purchased, if not United States dollars;
• if applicable, the designation and terms of the securities with which the warrants are issued and the number of warrants issued with each such security or each principal amount of such security;
• if applicable, the date on and after which the warrants and the related securities will be separately transferable;
• the number of shares of common stock purchasable upon the exercise of one warrant and the price at which these shares may be purchased upon such exercise;
• the effect of any merger, consolidation, sale or other disposition of our business on the warrant agreement and the warrants;
• the terms of any rights to redeem or call the warrants;
• any provisions for changes to or adjustments in the exercise price or number of securities issuable upon exercise of the warrants;
• the dates on which the right to exercise the warrants will commence and expire;
• the manner in which the warrant agreement and warrants may be modified;
• any material federal income tax consequences of holding or exercising the warrants;
• the terms of the common stock issuable upon exercise of the warrants; and
• any other specific terms, preferences, rights or limitations of or restrictions on the warrants.

Before exercising their warrants, holders of warrants will not have any of the rights of holders of our common stock including, the right to receive dividends, if any, or, payments upon our liquidation, dissolution or winding up or to exercise voting rights, if any.

Each warrant will entitle the holder to purchase common stock at the exercise price that we describe in the applicable prospectus supplement. Unless we otherwise specify in the applicable prospectus supplement, holders of the warrants may exercise the warrants at any time up to 5:00 P.M. Eastern Time on the expiration date that we set forth in the applicable prospectus supplement. After the close of business on the expiration date, unexercised warrants will become void.

Holders of the warrants may exercise the warrants by delivering the warrant certificate representing the warrants to be exercised together with specified information, and paying the required amount to the warrant agent in immediately available

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funds, as provided in the applicable prospectus supplement. We will set forth on the reverse side of the warrant certificate and in the applicable prospectus supplement the information that the holder of the warrant will be required to deliver to the warrant agent.

Upon receipt of the required payment and the warrant certificate properly completed and duly executed at the corporate trust office of the warrant agent or any other office indicated in the applicable prospectus supplement, we will issue and deliver the common stock purchased upon such exercise. If fewer than all of the warrants represented by the warrant certificate are exercised, then we will issue a new warrant certificate for the remaining amount of warrants. If we so indicate in the applicable prospectus supplement, holders of the warrants may surrender securities as all or part of the exercise price for warrants.

Any warrant agent will act solely as our agent under the applicable warrant agreement and will not assume any obligation or relationship of agency or trust with any holder of any warrant. A single bank or trust company may act as warrant agent for more than one issue of warrants. A warrant agent will have no duty or responsibility in case of any default by us under the applicable warrant agreement or warrant, including any duty or responsibility to initiate any proceedings at law or otherwise, or to make any demand upon us. Any holder of a warrant may, without the consent of the related warrant agent or the holder of any other warrant, enforce by appropriate legal action its right to exercise, and receive the securities purchasable upon exercise of, its warrants.

If a warrant holder exercises only part of the warrants represented by a single certificate, the warrant agent will issue a new warrant certificate for any warrants not exercised. Unless the prospectus supplement states otherwise, no fractional shares will be issued upon exercise of warrants, but we will pay the cash value of any fractional shares otherwise issuable.

The exercise price and the number of shares of common stock for which each warrant can be exercised will be adjusted upon the occurrence of events described in the warrant agreement, including the issuance of a common stock dividend or a combination, subdivision or reclassification of common stock.

Unless the prospectus supplement states otherwise, no adjustment will be required until cumulative adjustments require an adjustment of at least 1% in the exercise price. From time to time, we may reduce the exercise price as may be provided in the warrant agreement.

Unless the prospectus supplement states otherwise, if we enter into any consolidation, merger, or sale or conveyance of our property as an entirety, the holder of each outstanding warrant will have the right to acquire the kind and amount of shares, other securities, property or cash receivable by a holder of the number of shares of common stock into which the warrants were exercisable immediately prior to the occurrence of the event.

The warrant agreements may permit us and the warrant agent, if any, without the consent of the warrant holders, to supplement or amend the agreement in the following circumstances:

• to cure any ambiguity;
• to correct or supplement any provision which may be defective or inconsistent with any other provisions; or
• to add new provisions regarding matters or questions that we and the warrant agent may deem necessary or desirable and which do not adversely affect the interests of the warrant holders.

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PLAN OF DISTRIBUTION

Pursuant to General Instruction I.B.6 of Form S-3, we are permitted to use the registration statement of which this prospectus forms a part to sell a maximum amount of securities equal to one-third of the aggregate market value of our outstanding, publicly held voting and non-voting common equity in any 12 month period. We may, from time to time, offer and sell the securities registered hereby up to this maximum amount.

We may sell the securities described in this prospectus through underwriters or dealers, through agents, or directly to one or more purchasers or through a combination of these methods. The applicable prospectus supplement will describe the terms of the offering of the securities, including:

• the name or names of any underwriters, if any, and if required, any dealers or agents;
• the purchase price of the securities and the proceeds we will receive from the sale;
• any underwriting discounts and other items constituting underwriters' compensation;
• any discounts or concessions allowed or reallowed or paid to dealers; and
• any securities exchange or market on which the securities may be listed.

We may distribute the securities from time to time in one or more transactions at:

• a fixed price or prices, which may be changed;
• market prices prevailing at the time of sale;
• varying prices determined at the time of sale related to such prevailing market prices; or
• negotiated prices.

Only underwriters named in the prospectus supplement will be underwriters of the securities offered by the prospectus supplement.

If we use underwriters in the sale, they will acquire the securities for their own account and may resell the securities from time to time in one or more transactions at a fixed public offering price or at varying prices determined at the time of sale. We may offer the securities to the public through underwriting syndicates represented by managing underwriters or by underwriters without a syndicate. Any public offering price and any discounts or concessions allowed or reallowed or paid to dealers may change from time to time.

If we use a dealer in the sale of the securities being offered pursuant to this prospectus or any prospectus supplement, we will sell the securities to the dealer, as principal. The dealer may then resell the securities to the public at varying prices to be determined by the dealer at the time of resale.

We may sell the securities directly or through agents we designate from time to time. We will name any agent involved in the offering and sale of securities and we will describe any commissions we will pay the agent in the prospectus supplement.

We may authorize agents or underwriters to solicit offers by institutional investors to purchase securities from us at the public offering price set forth in the prospectus supplement pursuant to delayed delivery contracts providing for payment and delivery on a specified date in the future. We will describe the conditions to these contracts and the commissions we must pay for solicitation of these contracts in the prospectus supplement.

In connection with the sale of the securities, underwriters, dealers or agents may receive compensation from us or from purchasers of the securities for whom they act as agents in the form of discounts, concessions or commissions. Underwriters may sell the securities to or through dealers, and those dealers may receive compensation in the form of discounts, concessions or commissions from the underwriters or commissions from the purchasers for whom they may act as agents. Underwriters, dealers and agents that participate in the distribution of the securities, and any institutional investors or others that purchase securities directly and then resell the securities, may be deemed to be underwriters, and any discounts or commissions received by them from us and any profit on the resale of the securities by them may be deemed to be underwriting discounts and commissions under the Securities Act.

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Market Making, Stabilization and Other Transactions

Our common stock is listed on the NASDAQ Capital Market. Any common stock sold pursuant to a prospectus supplement will be eligible for listing and trading on the NASDAQ Capital Market, subject to official notice of issuance. Unless the applicable prospectus supplement states otherwise, each series of warrants will be a new issue and will have no established trading market. The applicable prospectus supplement will indicate if we elect to list a series of warrants on an exchange. Any underwriters that we use in the sale of securities may make a market in such securities, but may discontinue such market making at any time without notice. Therefore, we cannot assure you that the securities will have a liquid trading market.

Any underwriter also may engage in stabilizing transactions, syndicate covering transactions and penalty bids in accordance with Regulation M under the Securities Exchange Act of 1934, as amended. Stabilizing transactions involve bids to purchase the underlying security in the open market for the purpose of pegging, fixing or maintaining the price of the securities. Syndicate covering transactions involve purchases of the securities in the open market after the distribution has been completed in order to cover syndicate short positions.

Penalty bids permit the underwriters to reclaim a selling concession from a syndicate member when the security originally sold by the syndicate member is purchased in a syndicate covering transaction to cover syndicate short positions. Stabilizing transactions, syndicate covering transactions and penalty bids may cause the price of the security to be higher than it would be in the absence of the transactions. The underwriters may, if they commence these transactions, discontinue them at any time.

We, the underwriters or other agents may engage in derivative transactions involving the securities. These derivatives may consist of short sale transactions and other hedging activities. The underwriters or agents may acquire a long or short position in the securities, hold or resell the securities acquired and purchase options or futures on the securities and other derivative instruments with returns linked to or related to changes in the price of the securities. In order to facilitate these derivative transactions, we may enter into security lending or repurchase agreements with the underwriters or agents. The underwriters or agents may effect the derivative transactions through sales of the securities to the public, including short sales, or by lending the securities in order to facilitate short sale transactions by others. The underwriters or agents may also use the securities purchased or borrowed from us or others (or, in the case of derivatives, securities received from us in settlement of those derivatives) to directly or indirectly settle sales of the securities or close out any related open borrowings of the securities.

We may also make sales through the Internet or through other electronic means. Since we may from time to time elect to offer securities directly to the public, with or without the involvement of agents, underwriters or dealers, utilizing the Internet or other forms of electronic bidding or ordering systems for the pricing and allocation of such securities, you will want to pay particular attention to the description of that system we will provide in a prospectus supplement.

Such electronic system may allow bidders to directly participate, through electronic access to an auction site, by submitting conditional offers to buy that are subject to acceptance by us, and which may directly affect the price or other terms and conditions at which such security is sold. These bidding or ordering systems may present to each bidder, on a so-called "real-time" basis, relevant information to assist in making a bid, such as the clearing spread at which the offering would be sold, based on the bids submitted, and whether a bidder's individual bids would be accepted, prorated or rejected. Of course, many pricing methods can and may also be used.

Upon completion of such an electronic auction process, securities will be allocated based on prices bid, terms of bid or other factors. The final offering price at which securities would be sold and the allocation of securities among bidders would be based in whole or in part on the results of the Internet or other electronic bidding process or auction.

We may provide agents and underwriters with indemnification against particular civil liabilities, including liabilities under the Securities Act, or contribution with respect to payments that the agents or underwriters may make with respect to such liabilities. Agents and underwriters may engage in transactions with, or perform services for, us in the ordinary course of business. We will describe in the prospectus supplement the nature of any such relationship and the name of the parties involved.

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LEGAL MATTERS

The validity of the securities offered will be passed upon for us by Cozen O'Connor, Philadelphia, Pennsylvania.

The consolidated financial statements and schedule of Zoom Technologies, Inc. appearing in our Annual Report on Form 10-K for the year ended December 31, 2008 have been audited by UHY LLP, independent registered public accounting firm, as set forth in their report thereon, included therein, and incorporated herein by reference. Such consolidated financial statements and schedule are incorporated herein by reference in reliance upon the report of such firm given upon their authority as experts in accounting and auditing.

We have filed a registration statement on Form S-3 with the Securities and Exchange Commission in connection with this offering. We file annual, quarterly and current reports, proxy statements and other information with the Securities and Exchange Commission. You may read and copy the registration statement and any other documents we have filed at the Securities and Exchange Commission's Public Reference Room at 100 F Street, N.E., Washington, D.C. 20549. Please call the Securities and Exchange Commission at 1-800-SEC-0330 for further information on the Public Reference Room. Our Securities and Exchange Commission filings are also available to the public at the Securities and Exchange Commission's Internet site at www.sec.gov.

This prospectus is part of the registration statement and does not contain all of the information included in the registration statement. Whenever a reference is made in this prospectus to any of our contracts or other documents, the reference may not be complete and, for a copy of the contract or document, you should refer to the exhibits that are a part of the registration statement.

The Securities and Exchange Commission allows us to "incorporate by reference" into this prospectus the information we file with it, which means that we can disclose important information to you by referring you to those documents. Later information filed with the Securities and Exchange Commission will update and supersede this information.

We incorporate by reference the documents listed below, all filings filed by us pursuant to the Exchange Act after the date of the initial registration statement of which this prospectus forms a part prior to effectiveness of such registration statement, and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934 prior to the time that all securities covered by this prospectus have been sold; provided, however, that we are not incorporating any information furnished under either Item 2.02 or Item 7.01 of any current report on Form 8-K:

• Our Annual Report on Form 10-K for the year ended December 31, 2008.
• Our Current Reports on Form 8-K filed February 3, 2009 (two reports were filed on such date).
• The description of our common stock contained in our registration statement on Form 8-A filed on March 4, 2002, and any amendment or report filed for the purpose of updating that description.

An updated description of our common stock is included in this prospectus under "Description of Common Stock."

You may request a copy of these filings, at no cost, by contacting us at:

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March 16, 2009