Document:

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                                                                   Exhibit 10.15

SUMMARY OF LOANS BY ATX TELECOMMUNICATIONS SERVICES, INC. TO THOMAS GRAVINA AND
DEBRA BURUCHIAN

      During 1999 and 2000, the predecessors of ATX Telecommunications Services,
Inc., two limited partnerships, made loans to Thomas Gravina, the current
Co-President and a stockholder of ATX Telecommunications Services, Inc., and
Debra Buruchian, the other current Co-President and also a stockholder of ATX
Telecommunications Services, Inc., in the aggregate principle amounts of
$2,132,842.32 each. These loans have been satisfied.<PAGE>   1
                                                                 Exhibit 10.16

SUMMARY OF INDEBTEDNESS OF ATX TELECOMMUNICATIONS SERVICES, INC. TO MICHAEL KARP

      The predecessor entities of ATX Telecommunications Services, Inc.
currently have indebtedness to Michael Karp in the aggregate principle amount of
$3.6 million. Approximately $1.75 million of this amount was used to fund
operating expenses of ATX Telecommunications Services, Inc. The remaining $1.85
million was used to fund acquisitions of property, plant and equipment by ATX
Telecommunications Services, Inc. These loans have been retired.<PAGE>   1

                                                                 Exhibit 10.17

SUMMARY OF PROVISION OF SERVICES TO ATX TELECOMMUNICATIONS SERVICES, INC. BY
UNIVERSITY CITY HOUSING

      University City Housing, an entity controlled by Michael Karp, currently
provides general accounting, cash management, tax return preparation, payroll
and human resources services to ATX Telecommunications Services, Inc. ATX
Telecommunications Services, Inc. pays University City Housing approximately
0.38% of its gross annual receipts for providing these services. For the year
ended December 31, 1999, ATX Telecommunications Services, Inc. paid University
City Housing $501,000 for providing these services. In connection with the ATX
merger, University City Housing and post-merger CoreComm will enter into a
transition services agreement under which University City Housing will continue
to provide these services to post-merger CoreComm for a limited period of time.
The transition services agreement is more fully described in the section of the
joint proxy statement and prospectus entitled "The Merger Agreements -- The
Merger Agreement between CoreComm and ATX -- Related Agreements -- The
Transition Services Agreement."<PAGE>   1

                                                                   EXHIBIT 10.43

                               INPUT/OUTPUT, INC.
                              ANNUAL INCENTIVE PLAN

                           Effective November 3, 1999

                                     Purpose

            The purpose of the Input/Output, Inc. ("I/O") Annual Incentive Plan
   is to advance the interests of I/O and its stockholders by providing
   employees with annual incentive compensation which is tied to the achievement
   of preestablished and objective performance goals.

                                    ARTICLE I
                                   Definitions

            For the purpose of this Plan, unless the context requires otherwise,
the following terms shall have the meanings indicated:

            "Base Pay" means the gross annual base pay of a Participant
(exclusive of bonuses and Incentive Amounts and any compensation under any other
employee compensation or benefit plans of the Company) paid or to be paid, as
the case may be, to a Participant with respect to the Incentive Year in
question, according to the books and records of the Company and its
Subsidiaries.

            "Board" means the board of directors of the Company.

            "Book Equity" means an amount equal to the average Company
consolidated stockholders' equity for the Incentive Year, being the average of
the four quarters' stockholders equity amounts (each computed as beginning
stockholders' equity plus ending stockholders' equity for that quarter, divided
by two), where stockholders' equity shall include the amounts attributable to
common stock preferred stock, and retained earnings and shall be derived from
the Company's consolidated balance sheet as of the beginning and end of each
quarter during the Incentive Year, prepared in accordance with GAAP.

            "Committee" has the meaning assigned to it in Article II.

            "Company" means I/O, a Delaware corporation.

            "Employee" shall mean any regular full-time hourly or salaried
domestic employee of the Company or one of its Subsidiaries, excluding employees
covered by a collective bargaining agreement or any individuals classified as
independent contractors (even if a governmental agency or other entity would
classify such individuals differently).

            "GAAP" means those generally accepted accounting principles and
practices which are recognized as such by the American Institute of Certified
Public Accountants acting through the Accounting Principles Board or by the
Financial Accounting Standards Board or through other appropriate boards or
committees thereof and which are consistently applied for all periods so as to
properly reflect the financial condition and the results of operations of the
Company and its

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Subsidiaries, except that any accounting principle or practice required to be
changed by such Financial Accounting Standards Board (or other appropriate board
or committee of such board) in order to continue as a generally accepted
accounting principle or practice may so be changed.

            "Incentive Amount" means the amount payable to a Participant
calculated pursuant to Article IV of the Plan.

            "Incentive Pool" means the amount calculated pursuant to Article IV
from which the Incentive Amounts shall be paid.

            "Incentive Year" means the fiscal year of the Company and its
Subsidiaries with respect to which an Incentive Amount is calculated.

            "Participant" means an Employee who is eligible for participation in
the Plan and who, on the particular Payment Date, is, subject to Article V, then
employed by the Company or any of its Subsidiaries.

            "Payment Date" means the business day selected by the Committee upon
which the Committee shall make final Incentive Amount calculations in accordance
with Article IV, which shall be a date approximately sixty (60) days after the
end of the Incentive Year and, in any event, after the Company's independent
accounting firm issues its audit report on the Company's consolidated financial
statements with respect to the Incentive Year in question.

            "Plan" means the I/O Annual Incentive Plan, as it may be amended
from time to time.

            "Pool Percentage" shall be twenty percent (20%), unless otherwise
determined by the Committee in its sole discretion, or as otherwise provided
herein.

            "Profits Before Taxes" or "PBT" means with respect to a Payment
Date, the sum of (i) the net income, before provision for income taxes and
preferred stock dividends, of the Company and its Subsidiaries for the Incentive
Year in question determined by reference to the Company's audited consolidated
statement of earnings for such Incentive Year prepared in accordance with GAAP,
plus (ii) the total of all direct Incentive Amounts for the Participants under
the Plan accrued in determining such amount for such Incentive Year. In
determining the annual PBT, gains or losses from certain non-recurring or
extraordinary transactions, such as sales of assets (excluding regular sales
from inventory), reorganizations, acquisitions, divestitures or other capital or
financial transactions (as determined by the Committee in its sole discretion),
shall be excluded.

            "Return on Book Equity" means, unless otherwise specified herein or
determined by the Committee, an amount computed by multiplying the applicable
Return on Book Equity Percentage times Book Equity for the Incentive Year in
question.

            "Return on Book Equity Percentage" shall be eight percent (8%),
unless otherwise determined by the Committee in its sole discretion, or as
otherwise provided herein.

            "Subsidiary" means any corporation, 100% of the voting stock of
which is owned directly or indirectly (through other Subsidiaries) by the
Company.

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                                   ARTICLE II
                                 ADMINISTRATION

            Subject to the terms of this Article II, the Plan shall be
administered by the Compensation Committee (the "Committee") of the Board.
Subject to the terms hereof; the Committee shall interpret the Plan, prescribe,
amend, and rescind any rules and regulations necessary or appropriate for the
administration of the Plan, and make such other determinations and take such
other action as it deems necessary or advisable. In this regard, the Committee
may consider and give appropriate weight to input from representatives of
management of the Company regarding the contributions or potential contributions
to the Company or a Subsidiary of certain employees, or potential employees, of
the Company or any Subsidiary.

            The Committee shall have full authority to administer the Plan,
including authority to interpret and construe any provision of the Plan and to
adopt such rules and regulations for administering the Plan as it may deem
necessary Except as provided below, any interpretation, determination, or other
action made or taken by the Committee shall be final, binding, and conclusive on
all interested parties, including the Company and all Participants.

            During an Incentive Year, the Committee shall have discretion to
adjust Profits Before Taxes, Return on Book Equity Percentage, Pool Percentage
and percentage allocations of the Incentive Pool, provided that these
adjustments are made during the first six (6) months of an Incentive Year.

                                   ARTICLE III
                                   ELIGIBILITY

            All Employees shall be eligible to become a Participant in this Plan
after the completion of six (6) months of consecutive service with the Company
or a Subsidiary. Any Employee who is hired after the commencement of a Incentive
Year shall participate in the Plan on a pro rata basis (based on such Employee's
total days of service with the Company or a Subsidiary divided by 365), provided
that such Employee has first completed six (6) consecutive months of service
with the Company or Subsidiary. Employees who participate in this Plan may also
participate in other incentive or benefit plans of the Company or any
Subsidiary.

                                   ARTICLE IV
                                INCENTIVE AMOUNT

             Subject to and in accordance with the terms of this Plan, on each
    Payment Date, the Committee shall compute the Incentive Pool by reference to
    (I) Profits Before Taxes and (ii} Return on Book Equity, for the particular
    Incentive Year in question. The Incentive Amounts shall be calculated as
    follows:

                  (a) First, Profits Before Taxes shall be reduced by the Return
         on Book Equity amount

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                  (b) Second, the difference between Profits Before Taxes and
         the Return on Book Equity amount shall be multiplied by the Pool
         Percentage, with the resulting product being the Incentive Pool; the
         Incentive Pool shall be reduced by the Company's or a Subsidiary's
         portion of any FICA amounts required to be paid on the total Incentive
         Amounts;

                  (c) Third, provided that the Incentive Pool exceeds $500,000,
         each Participant shall be entitled to receive an Incentive Amount
         calculated as his pro rata portion of an amount equal to fifty percent
         (50%) of the Incentive Pool, with pro rata being computed on the basis
         of a Participant's Base Pay for the Incentive Year in question compared
         to the total Base Pay of all Participants for such Incentive Year;

                  (d) Fourth, the Committee shall allocate the remaining fifty
         percent (50%) of the Incentive Pool to the Employees in such manner as
         determined by the Committee in its sole discretion, or if Incentive
         Pool does not exceed $500,000, then the Committee shall have discretion
         to allocate the Incentive Pool to Employees in a manner determined in
         its sole discretion; and

                  (e) Notwithstanding the foregoing, with respect to the
         Incentive Years commencing on June 1, 1999 (Incentive Year 2000) and
         June 1, 2000 (Incentive Year 2001), the following adjustments shall be
         made for purposes of calculating the Incentive Pool: (i) for the
         Incentive Year commencing in 1999, Profits Before Taxes (including
         where Profits Before Taxes is a negative or loss amount) shall be
         increased by $32,000,000 and the Return on Book Equity Percentage shall
         be zero percent (0%); and (ii) for the Incentive Year commencing in
         2000, Profits Before Taxes (including where Profits Before Taxes is a
         negative or loss amount) shall be increased by $16,000,000 and the
         Return on Book Equity Percentage shall be four percent (4%); provided
         however that in any case, the minimum Incentive Pool amount with
         respect to each of the 2000 and the 2001 Incentive Years shall be
         $500,000.

                                    ARTICLE V
               PAYMENT OF INCENTIVE AMOUNTS AND GENERAL PROVISIONS

            5.1 Payment Dales. As a condition to eligibility for receipt of an
Incentive Amount with respect to any particular Incentive Year, a Participant
shall be required to be in the employ of the Company or one of its Subsidiaries
through the applicable Payment Date, unless (i) such Participant terminated his
or her employment during such period due to retirement from the Company and its
Subsidiaries in accordance with the standard retirement policies of the Company
and its Subsidiaries then in effect, (ii) the Participant, while in the employ
of the Company or one of its Subsidiaries, became totally and permanently
disabled (as that term is defined in Section 22(e) of the Internal Revenue Code
of 1986, as amended) or (iii) the Participant dies while employed by the Company
or a Subsidiary. In such cases, the Participant or his estate, if applicable,
shall be entitled to a pro rata portion of the Incentive Amount payable with
respect to that Participant and the applicable Incentive Year.

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            5.2 PARTIAL FISCAL YEARS. In the event that the Company and its
Subsidiaries adopt any different fiscal year which results in a fiscal year
having less than twelve months, the Committee shall, in its sole discretion,
award Incentive Amounts computed as provided in Article IV (but adjusted by the
Committee, based on its sole discretion, for such shortened fiscal year).

            5.3 NO RIGHTS TO INCENTIVE AMOUNT. The prospective recipient of an
Incentive Amount shall not have any rights with respect to any Incentive Amount,
or any portion thereof, until the Payment Date and only then until such
Incentive Amount is actually granted by the Committee to such Participant in
accordance with the terms of the Plan. The Incentive Amounts will only be paid,
if after consideration of such payment, the Company is not in default of any
material provision on outstanding debt as determined by the Committee.

                                   ARTICLE VI
                           AMENDMENT OR DISCONTINUANCE

            The Board may at any time and from time to time, without the consent
of the Participants, alter, amend, revise, suspend, or discontinue the Plan in
whole or in part;

                                   ARTICLE VII
                                      TERM

            The effective date of this Plan shall be November 3, 1999. Unless
sooner terminated by action of the Board, the Plan will terminate on May 31,
2010. Incentive Amounts under the Plan may not be granted after that date, but
Incentive Amounts granted before that date will continue to be effective in
accordance with their terms and conditions.

                                  ARTICLE VIII
                   RECAPITALIZATION, MERGER AND CONSOLIDATION

            The existence of this Plan and the Incentive Amounts granted
hereunder shall not affect in any way the right or power of the Company or its
stockholders to make or authorize any or all adjustments, recapitalizations,
reorganizations or other changes in the Company's capital structure or its
business, or any merger or consolidation of the Company, or any issue of bonds,
debentures, preferred or prior preference stocks ranking prior to or otherwise
affecting the Common Stock or the rights thereof (or any rights, options or
warrants to purchase same), or the dissolution or liquidation of the Company, or
any sale or transfer of all or any part of its assets or business, or any other
corporate act or proceeding, whether of a similar character or otherwise.

                                   ARTICLE IX
                            MISCELLANEOUS PROVISIONS

            9.1 NON-ASSIGNABILITY. Subject to Section 5.1 hereof, no interest of
a Participant in any Incentive Amount awarded under the Plan may be transferred,
alienated, assigned or encumbered other than by will or pursuant to the laws of
descent and distribution.

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            9.2 NO RIGHT TO CONTINUE EMPLOYMENT. Nothing in the Plan confers
upon any employee the right to continue in the employ of the Company or
interferes with or restricts in any way the right of the Company to discharge
any employee at any time (subject to any contract rights of such employee).

            9.3 TAX REQUIREMENTS. The Company (and, where applicable, its
Subsidiaries) shall have the power and the right to deduct or withhold, or
require a Participant to remit to the Company an amount sufficient to satisfy
all applicable taxes required by law to be withheld with respect to any payment
of any Incentive Amount to a Participant.

            9.4 INDEMNIFICATION OF BOARD AND COMMITTEE. No member of the Board
or the Committee, nor any officer, employee or agent of the Company acting on
behalf of the Board or the Committee, shall be personally liable for any action,
determination, or interpretation taken or made in good faith with respect to the
Plan, and all members of the Board or the Committee and each and every officer,
employee or agent of the Company acting on their behalf shall, to the fullest
extent permitted by law, be fully indemnified and protected by the Company in
respect of any such action, determination or interpretation. Each member of the
Board and the Committee shall, in the performance of his or her duties under the
Plan, be fully protected in relying in good faith upon the audited and unaudited
financial statements of the Company as contemplated by the terms of the Plan.

            9.5 EFFECT ON PARTICIPATION. The grant of an Incentive Amount to a
Participant shall not be deemed either to entitle the Participant to, or to
disqualify the Participant from, as the case may be, participation in any other
future grant of Incentive Amounts under the Plan or otherwise, or in any other
compensation or benefit plan of the Company or in any of its Subsidiaries
currently existing or hereafter established.

            9.6 OTHER COMPENSATION AGREEMENTS. Nothing contained in this Plan
shall prevent the Board from adopting other or additional compensation
arrangements, subject to stockholder approval if such approval is required; and
such arrangements may be either generally applicable or applicable only in
specific cases.

            9.7 GENDER AND NUMBER. Where the context permits, words in the
masculine gender shall include the feminine and neuter genders, the plural form
of a word shall include the singular form, and the singular form of a word shall
include the plural form.

                                    ARTICLE X
                             UNFUNDED STATUS OF PLAN

            The Plan is intended to constitute an "unfunded" plan for incentive
compensation. With respect to any Incentive Amounts granted but not yet paid to
a Participant by the Company. nothing contained herein shall give any such
Participant any rights that are greater than those of a general unsecured
creditor of the Company. In its sole discretion, the Committee may authorize the
creation of. trusts or other arrangements to satisfy the Plan provisions
concerning payments with respect to awards of Incentive Amounts; provided,
however, that the creation or existence of such trusts or other arrangements is
consistent with the unfunded status of the Plan.

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                 EXECUTED this         day of            , 1999
                              --------       ------------

                                  INPUT/OUTPUT, INC

                                  By:
                                     ---------------------------------------
                                  Name:
                                       -------------------------------------
                                  Title:
                                        ------------------------------------

Attest:

-------------------------
Secretary

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