
<PAGE>
 
                                                                    EXHIBIT 99.2

                               MASTER REVOLVING
                                LINE OF CREDIT
                                PROMISSORY NOTE

US$35,000,000                                           December 14, 1998

     FOR VALUE RECEIVED, and intending to be legally bound hereby, CABLE DESIGN
TECHNOLOGIES INC., a Washington corporation (the "Borrower"), hereby promises to
pay to the order of ABN AMRO BANK N.V. (which, together with its endorsees,
successors and assigns, is referred to herein as the "Bank"), at its office
located at One PPG Place, Suite 2950, Pittsburgh, Pennsylvania 15222-5400 (or at
such other place of payment designated by the holder hereof to the Borrower),
the lesser of (i) the principal sum of THIRTY FIVE MILLION UNITED STATES DOLLARS
(US$35,000,000) or (ii) the aggregate unpaid principal balance of all advances
made by Bank to or for the benefit of Borrower (each, an "Advance") pursuant to
that letter agreement, dated as of the date hereof, between Borrower and Bank
(as amended, modified, extended, supplemented, or the like from time to time,
the "Agreement"), in lawful money of the United States of America ("US") in
immediately available funds, payable at the earlier of December 12, 1999 (the
"Termination Date"), or as otherwise set forth in the Agreement.  Capitalized
terms, not otherwise defined herein, shall have the respective meanings ascribed
to them by the Agreement.

     Borrower hereby further promises to pay to the order of Bank, at the place
of payment, interest on the unpaid principal amount of each Advance from the
date such Advance is made until the maturity thereof (whether at stated
maturity, by acceleration, or otherwise), at one or another of the following
interest rate options (each an "Interest Rate Option") which Borrower shall
select in accordance with the terms hereof: (a) upon the selection of a Base
Rate option (the "Base Rate Option"), a fluctuating rate of interest per annum
equal to the Base Rate of Bank (as hereinafter defined), or (b) upon the
selection of a LIBOR option (the "LIBOR Option"), the Applicable Margin (as
hereinafter defined) plus LIBOR (as hereinafter defined).  For each new Advance,
and with respect to each outstanding Advance for which an applicable Interest
Period is expiring, Borrower shall select either a Base Rate Option or a LIBOR
Option to be applicable to such Advance; such selection shall be communicated to
Bank by irrevocable notice (in writing by telex, telecopier, telegram, cable, or
delivery) (A) which, in the case of a LIBOR Option selection, shall be provided
to Bank by 11:00 a.m. (Pittsburgh time) three (3) Business Days prior to the
date on which the relevant new Advance is proposed to be made or three (3)
Business Days prior to the last day of the then current Interest Period
applicable to such outstanding Advance, and (B) which, in the case of a Base
Rate Option selection, shall be provided to Bank no later than 11:00 a.m.
Pittsburgh time on the Business Day on which such requested new Advance is
proposed to be made or on which an Interest Period for such outstanding Advance
is to expire.  If no Interest Rate Option is timely selected at the end of any
Interest Period for an Advance, Borrower shall be deemed to have selected a Base
Rate Option for such Advance.  In no event shall the interest rate(s) applicable
to principal outstanding hereunder exceed the maximum rate of interest allowed
by applicable law, as amended from time to time; any payment of interest or in
the nature of interest in excess of such limitation shall be credited as a
payment of principal unless Borrower requests the return of such amount.

     A Base Rate Option applicable to an existing Advance may at any time be
converted to a LIBOR Option for such Advance upon the selection of an Interest
Period therefor and the giving of appropriate prior irrevocable notice (in
writing by telex, telecopier, telegram, cable, or delivery) of such conversion
by Borrower to Bank by 11:00 a.m. (Pittsburgh time) three (3) Business Days
prior to the date of conversion, subject to the terms hereof.  Unless the
applicable breakfunding fees (referred to in the 17th paragraph hereof) are
paid, a LIBOR Option applicable to an existing Advance may be converted to a
Base Rate Option only on the last Business Day of the Interest Period applicable
to such Advance subject to appropriate prior notice thereof by Borrower to Bank
in accordance with the terms hereof.

     The making of Advances, the conversion of a Base Rate Option to a LIBOR
Option with respect to an Advance, and the continuation of the LIBOR Option upon
the last day of an Interest Period for an Advance may occur only on a Business
Day (as hereinafter defined).
<PAGE>
 
     Interest on each Base Rate Option Advance shall be due and payable in
arrears on the last Business Day of each January, April, July, and October
hereafter and at maturity and after maturity on demand.  Interest on each LIBOR
Option Advance shall be due and payable in arrears on the last day of each
Interest Period for such Advance (except that, with respect to Advances having
an Interest Period of six months, interest shall be paid as if a three month
Interest Period were applicable thereto), commencing on the first such date to
occur after the date hereof, and at maturity, after maturity on demand, and on
the date of any payment of any such Advance on the amount paid.  The outstanding
principal amount of a LIBOR Option Advance may be prepaid, in whole or in part,
at the end of an Interest Period applicable thereto; without the prior written
consent of Bank, no Advance subject to the LIBOR Option may be prepaid prior to
the date of the maturity thereof (at stated maturity, by acceleration, or
otherwise), except on the last Business Day of the Interest Period therefor (and
only upon three (3) Business Days prior irrevocable notice (in writing by telex,
telecopier, telegram, cable, or delivery) from Borrower to Bank thereof);
provided, however, that all pre-payments of a LIBOR Option Advance shall be in a
minimum principal amount of US$500,000 and a multiple of US$500,000, or such
lesser principal balance of the LIBOR Option Advance outstanding.  The
outstanding principal amount of a Base Rate Option Advance may be pre-paid, in
whole or in part, at any time; provided, however, that pre-payments of the
outstanding principal amount of any Base Rate Option Advance shall be in a
minimum principal amount of $500,000 or such lesser principal balance of the
Advance outstanding.  At no time shall more than four (4) Advances to which the
LIBOR Option applies be outstanding at any one time.

     Borrower hereby further promises to pay to the order of the Bank, on
demand, at the place of payment, interest on the unpaid principal amount of each
Advance after maturity thereof (whether at stated maturity, by acceleration, or
otherwise), at a rate per annum equal to the higher (redetermined daily) of (i)
two percent (2%) per annum in excess of the interest rate in effect just prior
to maturity, or (ii) the sum of two percent (2%) per annum and the Base Rate of
the Bank from time to time in effect.

     Borrower hereby further promises to pay to Bank a nonrefundable facility
fee, (as described herein the "Facility Fee") for the period from and including
the date hereof to the earlier of indefeasible and final payment in full of this
Promissory Note or the Termination Date, equal to the product of (a) the
Facility Fee Rate (as hereinafter defined) and (b) the average daily amount of
the Facility (regardless of usage) during the period for which such Facility Fee
is calculated (computed on the basis of a year of 360 days for the actual number
of days elapsed), payable quarterly in arrears on the last Business Day of each
January, April, July, and October and on the Termination Date.  Such payments
shall commence on January 31, 1999, and such first payment shall be for the
period from the date hereof through January 31, 1999.

     Bank is hereby authorized by Borrower to record on its books and records,
the principal amount and borrowing date of each Advance made hereunder, the
interest rate, Interest Period,  and interest payment dates applicable thereto,
the maturity date thereof and all payments of principal and interest made
thereon.  The books and records of Bank shall be conclusive and binding upon the
Borrower, absent manifest error.

     All payments due hereunder shall be made by the Borrower to the holder
hereof no later than 11:00 a.m. Pittsburgh time at the place of payment, in US
dollars and in funds immediately available and freely transferable at the place
of payment, free and clear of, and without deduction for, any present or future
taxes, levies, withholding, or similar deductions of any nature whatsoever
("Deductions").  Payments received after such time shall be deemed received by
the holder hereof on the next succeeding Business Day at such place of payment.
In the event that the Borrower is compelled for any reason to make any
Deductions, it shall pay to the holder hereof such amounts (after giving effect
to all Deductions on all additional payments to be made hereunder) as will
result in the receipt by the holder hereof of the amount such holder would have
received had no such Deductions been required to be made.  If any payment shall
fall due hereunder on a day that is not a Business Day, payment shall be 

                                       2
<PAGE>
 
made on the next succeeding Business Day and interest thereon shall be payable
for such extended time, provided, however, that with respect to any payment of
interest based upon the LIBOR Option, if such succeeding Business Day shall fall
into a new calendar month, payment shall be made on the next preceding Business
Day. The Bank's determination of LIBOR and the Base Rate as provided herein
shall be conclusive, absent manifest error.

     "Applicable Margin" shall herein mean, for any day with respect to an
Advance subject to the LIBOR Option, the applicable basis points per annum set
forth below in the Pricing Grid under the caption "Applicable LIBOR Margin" and
corresponding to the Leverage Ratio then existing at the time of determination,
provided that the Applicable Margin shall be adjusted (retroactively if
necessary) as of the first day of the month following the date on which the Bank
is to receive the financial statements required to be delivered to Bank pursuant
to the incorporation into the Agreement of Sections 6.1(a), 6.1(b), and 6.1(e)
of the Existing Credit Agreement, and provided further that the Applicable
Margin commencing as of the date hereof shall be determined on the basis of
those financial statements prepared or to be prepared as of October 31, 1998.

                                  PRICING GRID
                                        
<TABLE>
<CAPTION>
---------------------------------------------------------------
                 (basis points per annum)
--------------------------------------------------------------------------------------------------------
             Leverage Ratio                        Facility Fee                     Applicable
                                                       Rate                        LIBOR Margin
--------------------------------------------------------------------------------------------------------
<S>                                                <C>                             <C>
Greater than 3.0x & less than or equal                 20.0                           105.0
 to 3.5x                                               
--------------------------------------------------------------------------------------------------------
Greater than 2.7x & less than or equal                 20.0                            92.5
 to 3.0x                                               
--------------------------------------------------------------------------------------------------------
Greater than 2.0x & less than or equal                 15.0                            85.0
 to 2.7x                                               
--------------------------------------------------------------------------------------------------------
Greater than 1.25x & less than or equal                15.0                            72.5
 to 2.0x                                               
--------------------------------------------------------------------------------------------------------
Greater than 0.75x & less than or equal                15.0                            60.0
 to 1.25x                                              
--------------------------------------------------------------------------------------------------------
Less than or equal to 0.75x                            10.0                            52.5
--------------------------------------------------------------------------------------------------------
</TABLE>

     "Base Rate" shall herein mean that fluctuating rate of interest equal to
the higher (redetermined daily) of (i) the per annum rate of interest announced
by the Bank from time to time at its principal office in Chicago as its prime
rate for US dollar loans (with any change in such prime rate to become effective
as of the start of business on the date on which such prime rate change shall be
made), or (ii) the per annum rate of interest at which overnight federal funds
are from time to time offered to the Bank by any bank in the interbank market in
an amount equal to the principal amount outstanding of such Advance, plus one-
half of one percent (0.5%) per annum.  Interest shall accrue on any Advance
hereunder that will be outstanding for less than a one month Interest Period at
a rate equal to the Base Rate.  Interest will be calculated on the basis of the
actual number of days elapsed over a year of 365 days.

     "Facility Fee Rate" shall herein mean for any day the applicable basis
points per annum set forth on the Pricing Grid above under the caption "Facility
Fee Rate" and corresponding to the Leverage Ratio then existing at the time of
determination, provided that the Facility Fee Rate shall be adjusted
(retroactively if necessary) as of the first day of the month following the date
on which the Bank is to receive the financial statements required to be
delivered to Bank pursuant to the incorporation into the Agreement of Sections
6.1(a), 6.1(b), and 6.1(e) of the Existing Credit Agreement, and provided
further that the Facility Fee Rate commencing as of the date hereof shall be
determined on the basis of those financial statements prepared or to be prepared
as of October 31, 1998.

                                       3
<PAGE>
 
     "Interest Period" shall herein mean successive one-month, three-month, or
six-month periods (as selected from time to time by the Borrower by irrevocable
notice (in writing by telex, telecopier, telegram, cable, or delivery) provided
to the Bank by 11:00 a.m. (Pittsburgh time) three (3) Business Days prior to the
first day of each respective Interest Period) commencing on the date of a new
Advance subject to the LIBOR Option or commencing on the date on which a Base
Rate Option applicable to an Advance is converted to a LIBOR Option or
commencing on the date on which the LIBOR Option is continued for an Advance for
which the previous Interest Period is expiring; provided that: (i) each such
one-month, three-month, or six-month period occurring after the initial such
period shall commence on the day on which the next preceding period expires;
(ii) no Interest Period for any Advance shall be selected that would expire
after the Termination Date; and (iii) if for any reason the Borrower shall fail
to timely select an Interest Period for an Advance to which the LIBOR Option is
to apply, then it shall be deemed to have selected a one-month Interest Period,
subject to clause (ii).

     "Leverage Ratio" shall be used herein as defined in the Existing Credit
Agreement.

     "LIBOR" shall herein mean with respect to an Advance to which the LIBOR
Option applies for any Interest Period, the per annum rate of interest
determined by Bank by dividing (the resulting quotient rounded upward to the
nearest 1/16th of 1% per annum) (i) the rate of interest per annum at which US
dollar deposits of an amount comparable to the amount of such Advance and for a
period equal to the relevant Interest Period are offered generally to the Bank
in the London interbank market at 11:00 a.m. (London time) two Business Days
prior to the commencement of such Interest Period, with such rate to remain
fixed for such Interest Period, by (ii) a number equal to 1.00 minus the Reserve
Percentage (as hereinafter defined).  LIBOR shall be adjusted with respect to
any Advance subject to the LIBOR Option as of the effective date of any change
in the Reserve Percentage.

     "Reserve Percentage" shall herein mean the maximum percentage (expressed as
a decimal rounded upward to the nearest 1/100th of 1%), as determined by Bank,
which is in effect during any relevant period: (i) as prescribed by the Board of
Governors of the Federal Reserve System (or any successor) (the "Board") for
determining the reserve requirements (including supplemental, marginal, and
emergency reserve requirements and without benefit of or credit for proration,
exceptions, or offsets which may be available to Bank from time to time under
Regulation D of the Board) with respect to eurocurrency funding (currently
referred to as "Eurocurrency Liabilities" by Regulation D of the Board); and
(ii) to be maintained by Bank as required for reserve liquidity, special
deposit, or a similar purpose by any governmental or monetary authority of any
country or political subdivision thereof (including any central bank), against
(A) any category of liabilities that includes deposits by reference to which
LIBOR is to be determined, or (B) any category of extension credit or other
assets that includes any Advance to which the LIBOR Option applies.

     If, for any reason (including as a result of any Event of Default), any
Advance subject to the LIBOR Option is paid or prepaid in whole or in part on a
day other than the last day of the Interest Period therefor or if any request
for an Advance subject to the LIBOR Option, or for the continuation of or
conversion to the LIBOR Option with respect to an Advance, is revoked or denied
(expressly, by later inconsistent notices, or otherwise), the Borrower shall
indemnify the Bank against any loss, cost, or expense (including loss of margin,
loss or expense incurred in liquidating or redeploying deposits from third
parties or incurred in terminating or unwinding any contracts or incurred in
connection with funds acquired or to be acquired to fund or maintain Advances)
incurred or sustained by Bank as a consequence.

     If the Bank shall have determined, in good faith (which determination shall
be conclusive, absent manifest error), prior to the commencement of any Interest
Period that (a) US Dollar deposits of sufficient amount and maturity for funding
any Advance are not available to the Bank in the London interbank market in the
ordinary course of business, or (b) by reason of circumstances affecting the
relevant market, adequate and fair means do not exist for ascertaining the rate
of interest to be applicable to an 

                                       4
<PAGE>
 
Advance, the Bank will promptly notify the Borrower thereof and no such Advance
will be made or, if already made, such Advance shall be immediately due and
payable on the last Business Day of the then existing Interest Period applicable
thereto, all without further demand, presentment, protest or notice of any kind,
all of which are hereby waived by the Borrower for all purposes hereof. If,
after the date hereof, the introduction of, or any change in, any applicable
law, treaty, rule, regulation or guideline or in the interpretation or
administration thereof by any governmental authority or any central bank or
other fiscal, monetary or other authority having jurisdiction over the Bank or
its lending office, shall, in the opinion of counsel to the Bank, make it
unlawful for the Bank to make or maintain any LIBOR Option Advance, then the
Bank shall promptly notify the Borrower thereof and no such Advance will be made
or, if already made, such Advance shall be immediately due and payable on the
last Business Day of the then existing Interest Period applicable thereto or on
such earlier date as required by law, all without further demand, presentment,
protest or notice of any kind, all of which are hereby waived by the Borrower.

     If any law, rule, or regulation or any action of any judicial,
administrative, or other governmental authority of any jurisdiction or political
subdivision thereof (whether or not having the force of law) adopted or taken
after the date hereof:

     (i)  subjects Bank to any tax or changes the basis of taxation with respect
     to this Promissory Note (except for taxes on the overall net income of
     Bank), or (ii) imposes, modifies, or deems applicable (A) any reserve,
     special deposit, or similar requirement against credits or commitments to
     extend credit extended by, or assets (funded or contingent) of, deposits
     with or for the account of, or other acquisitions of funds by, Bank or any
     affiliate of Bank involved in any Advance under this Promissory Note (any
     "Bank Affiliate"), or (B) any capital adequacy or similar requirement (x)
     against assets (funded or contingent) of, or credits or commitments to
     extend credit extended by, Bank or any Bank Affiliate, or (y) otherwise
     applicable to the obligations arising in connection with this Promissory
     Note,

and the result of any of the foregoing is to increase the cost to, reduce the
income receivable by, or impose any expense (including loss of margin) upon Bank
or any Bank Affiliate with respect to this Promissory Note (or, in the case of
any capital adequacy or similar requirement, to have the effect of reducing the
rate of return on Bank's or its holding company's capital, taking into
consideration Bank's and its holding company's customary policies with respect
to capital adequacy) by an amount which Bank in its sole discretion deems to be
material, Bank shall from time to time notify Borrower in writing of the amount
determined in good faith (using any averaging and attribution methods employed
in good faith) by Bank (which determination shall be conclusive absent manifest
error) to be necessary to compensate Bank or any Bank Affiliate (or its holding
company) for such increase in cost, reduction of income, or additional expense;
and, such amount shall be due and payable by Borrower to Bank ten (10) Business
Days after such notice is given.  Such written notice shall contain a
description of the matters giving rise to Bank's charge under this paragraph,
including such calculations as are necessary under the circumstances and in
sufficient detail to allow Borrower to reasonably understand the nature and
basis for such charge and the calculation of the amount thereof.  In no event,
however, shall Borrower be required to pay any amount otherwise required by this
paragraph if such amount relates to a period which ended more than ninety (90)
days prior to receipt by Borrower of such notice from Bank.

     This Promissory Note is the Note referred to in, and is entitled to the
benefits of, the Agreement and the other Loan Documents referred to therein.
Reference is made to the Agreement for a description of the relative rights and
obligations of Borrower and Bank, including rights and obligations of
prepayment, collateral (if any) securing payment hereof, events of default, and
rights of acceleration of maturity in the event of default.

                                       5
<PAGE>
 
     No delay on the part of the holder hereof in exercising any of its options,
powers, or rights, or partial or single exercise thereof, shall constitute a
waiver thereof.  The options, powers, and rights specified herein of the holder
hereof are in addition to those otherwise created or permitted by law, the
Agreement, and the other Loan Documents.  There are no claims, set-offs, or
deductions of any nature as of the date hereof that could be made or asserted by
Borrower against Bank or against any amount due or to become due under this
Promissory Note; all such claims, set-offs, or deductions are hereby waived.
Telecopy transmission to Bank of the signature page of this Promissory Note
purporting to be signed on behalf of Borrower shall constitute effective and
binding execution and delivery hereof by Borrower.  This Promissory Note shall
be governed by and construed in accordance with the laws of the Commonwealth of
Pennsylvania, without giving effect to conflict of laws principles.

     IN WITNESS WHEREOF and intending to be legally bound hereby, the Borrower
has executed this Promissory Note as of the date hereof by its duly authorized
officer with the intention that it constitute a sealed instrument.

                              CABLE DESIGN TECHNOLOGIES INC.



                              By:                                       (SEAL)
                                 Name:
                                 Title:

                                       6
