SERIES B DEBENTURE

THE SECURITIES OFFERED HEREBY HAVE NOT BEEN AND WILL NOT BE REGISTERED UNDER THE
SECURITIES ACT OF 1933, AS AMENDED,  AND THE RULES AND  REGULATIONS  PROMULGATED
THEREUNDER  (THE  "1933  ACT"),  AND MAY ONLY BE  OFFERED  OR SOLD  PURSUANT  TO
REGISTRATION  UNDER OR AN EXEMPTION FROM THE  REGISTRATION  REQUIREMENTS  OF THE
1933 ACT.


                  7% CONVERTIBLE DEBENTURE DUE OCTOBER 15, 1998


$_________________                                              October 15, 1996


         FOR VALUE RECEIVED,  INTELECT COMMUNICATIONS SYSTEMS LIMITED, a Bermuda
company     (the      "Company"),      hereby     promises     to     pay     to
_____________________________,  or registered  assigns (the "Holder") on October
15, 1998 (the  "Maturity  Date"),  the principal  amount of  ___________________
($______________) and to pay interest in cash on the principal amount hereof, in
such  amounts,  at such times and on such terms and  conditions as are specified
herein.  This  Debenture  (this  "Debenture")  is one of two Series B Debentures
issued in an aggregate  principal amount of $5,000,000  pursuant to that certain
Convertible  Securities  Agreement  executed  by the  Holder,  the  Company  and
__________________ dated October 15, 1996 (the "Agreement").

ARTICLE 1.        INTEREST.

         The Company shall pay interest on the unpaid  principal  amount of this
Debenture at the rate of Seven Percent (7%) per year,  payable in cash,  payable
quarterly  in arrears on each March 31, June 30,  September  30 and December 31,
commencing  March 31, 1997 (which  initial  payment shall be due April 15, 1997)
until the principal  hereof is paid in full or has been  converted.  Interest on
this Debenture shall accrue from the most recent date to which interest has been
paid or, if no interest has been paid,  from the date hereof.  Interest shall be
computed on the basis of the actual  number of days elapsed  during any interest
calculation period in a 360-day year of twelve 30-day months.

ARTICLE 2.        METHOD OF PAYMENT.

         The Company shall pay the  principal of and interest on this  Debenture
in  United   States   dollars.   Interest   shall  be  paid  to  the  holder  at
__________________________.  Principal shall be paid in the manner  described in
that  certain  Book  Entry  Transfer  Agent   Agreement  (the  "Transfer   Agent
Agreement") among the Company, the Holder, __________________ and American Stock
Transfer & Trust  Company,  the Company's  stock  transfer  agent (the "Transfer
Agent").  Interest and principal  payments shall be subject to  withholding  (if
any) under applicable United States Federal Internal Revenue

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Service Regulations.

ARTICLE 3.        CONVERSION.

         SECTION 3.1.  CONVERSION PRIVILEGE

         (a) The Holder of this Debenture  shall have the right,  exercisable at
one or more times, at its option,  to convert all or a portion of this Debenture
into common  shares,  par value $.01 per share (U.S.),  of the Company  ("Common
Shares"  or  "Common  Stock") at the times  hereafter  specified.  The number of
Common Shares  issuable upon the  conversion of this  Debenture is determined by
dividing the principal amount hereof to be converted by the Conversion Price (as
defined in paragraph (b) of this Section 3.1 below) in effect on the  conversion
date and rounding the result to the nearest 1/100th of a share. Upon conversion,
all accrued and unpaid interest will be paid to the Holder in cash.

         (b) All or any portion of this  Debenture is  convertible  at any time,
and from time to time as follows:  One-third  (1/3) of the principal  balance of
all Debentures  issued to Holders as described in Section 7.1 hereafter shall be
convertible  beginning  sixty  (60) days  after the date of this  Debenture;  an
additional  one-third  (1/3) of the  principal  balance  of all such  Debentures
issued to the Holders shall be  convertible  beginning 90 days after the date of
such Debentures;  and the final one-third (1/3) of the principal  balance of all
such  Debentures  issued to the Holders shall be convertible  beginning 120 days
after  the  date of such  Debentures;  provided,  that  if the  Company  has not
effected  the  registration  of the Common  Shares into which this  Debenture is
convertible on or before the expiration of the sixty (60) day period  referenced
above,  one-half (1/2) of the principal  balance of all the Debentures  shall be
convertible  at  such  time  and  the  remaining   principal  balance  shall  be
convertible  ninety (90) days after the date hereof.  The conversion price shall
be the  lesser of (A) Twelve and  No/100  Dollars  ($12.00)  per share of Common
Stock or (B) the product of (i) the current  market price of the Common Stock on
the conversion date  multiplied by (ii) eighty two and one-half  percent (82.5%)
(the "Formula Price");  provided,  if the conversion date is a date on or before
the 90th day following the date of this Debenture, the Conversion Price shall be
the greater of the Formula Price of the Common Stock on the  conversion  date or
Four and 50/00 Dollars ($4.50) per share of Common Stock (such  applicable price
being hereafter referred to as the "Conversion Price").

         (c) In the  event  any  Debenture  remains  outstanding  on the  second
anniversary of the date hereof,  the unconverted  portion of such Debenture will
automatically  be  converted  into Common  Shares on such date in the manner set
forth in this Section 3.1;  provided (i) an Event of Default does not then exist
under this  Debenture  and (ii) a  registration  statement  as  contemplated  by
Section 4 of the Agreement is effective  with respect to the sale by the Holders
of shares of Common Stock issuable upon conversion

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of this Debenture.

         (d) At any time, and from time to time, the Company, at its option (the
"Redemption Option"),  may redeem this Debenture at the Agreed Redemption Amount
(which shall mean the product of the remaining principal amount of the Debenture
multiplied by 117.5%,  plus accrued and unpaid interest thereon).  Any notice of
exercise of the Redemption Option (a "Redemption  Notice") shall be delivered in
writing to Holder and shall be  irrevocable  when  delivered.  The Company shall
not,  however,  be entitled  to issue a  Redemption  Notice with  respect to any
portion of the Debenture for which Holder has  previously  delivered a Notice of
Conversion as contemplated by this Debenture,  and any such Notice of Conversion
delivered  after the Company  issues a Redemption  Notice shall be invalid.  The
Company shall pay the Agreed Redemption Amount in the manner contemplated in the
Transfer Agent  Agreement  upon exercise of the Redemption  Option within thirty
(30) days of the  delivery  of such  Redemption  Notice.  During the  Redemption
Period,  the Company  shall comply with all terms,  conditions  and covenants of
this  Debenture  (including,  without  limitation  timely payment of accrued and
unpaid  interest).  Subject to the  foregoing,  Holder's  option to convert this
Debenture  into  shares of Common  Stock shall be abated  during the  Redemption
Period.

         SECTION  3.2.  CONVERSION  PROCEDURE.  To convert this  Debenture  into
Common  Shares,  the Holder  must  complete  and sign the  Notice of  Conversion
attached hereto and deliver the same  (including  delivery via facsimile) to the
Transfer  Agent.  The date upon which the Transfer  Agent receives the completed
Notice of Conversion (by recognized overnight courier, hand-delivery,  facsimile
or otherwise) is the conversion date. Within two (2) business days after receipt
of the Notice of Conversion  as aforesaid,  the Company shall cause the Transfer
Agent to deliver a  certificate  for the number of full Common  Shares  issuable
upon the conversion and a check for any fraction of a share. The person in whose
name the  certificate  representing  Common Shares is to be registered  shall be
treated  as a  shareholder  of record on and after  the  conversion  date.  Upon
conversion,  unpaid interest on the converted  portion of the Debenture shall be
paid in cash by the Company.  If one person  converts more than one Debenture at
the same time, the number of full shares  issuable upon the conversion  shall be
based on the total principal amount of Debentures converted. Notwithstanding the
foregoing, the conversion right of the Holder set forth herein shall be limited,
solely to the extent required, from time to time, such that in no instance shall
the  maximum  number of Common  Shares  into which the Holder may  convert  this
Debenture exceed, at any one time, an amount equal to the remainder of (i) 4.99%
of the then  issued  and  outstanding  shares  of  Common  Stock of the  Company
following  such  conversion,  minus (ii) the number of shares of Common Stock of
the Company then held by the Holder.


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         SECTION  3.3.   FRACTIONAL  SHARES.  The  Company  shall  not  issue  a
fractional share of Common Stock upon the conversion of this Debenture. Instead,
the Company shall pay in lieu of any fractional  share the cash value thereof at
the then current  market price of the Common Shares as determined  under Section
3.7 below.

         SECTION  3.4.   TAXES  ON   CONVERSION.   The  Company  shall  pay  any
documentary,  stamp or similar  issue or transfer tax due on the issue of Common
Shares upon the conversion of this Debenture.  However, the Holder shall pay any
such tax which is due  because  such  shares are issued in a name other than its
name.

         SECTION 3.5. COMPANY TO RESERVE STOCK. The Company shall reserve out of
its  authorized  but unissued  Common  Shares enough Common Shares to permit the
conversion in full of this Debenture. All Common Shares which may be issued upon
the conversion hereof shall be fully paid and nonassessable.

         SECTION 3.6.  RESTRICTIONS  ON TRANSFER.  This Debenture and the Common
Shares issuable upon the conversion  hereof have not been  registered  under the
Securities  Act of 1933 (the "Act") and have been sold  pursuant to an exemption
under the Act. The Debenture may not be transferred or resold except pursuant to
registration under or an exemption from the Act.

         SECTION 3.7.  CURRENT MARKET PRICE.

         (a) As used herein, the current market price per share of Common Shares
on any date is the  average of the  closing  bid price of the  Common  Shares on
NASDAQ (or on such  exchange as the Common  Shares are then listed) for five (5)
consecutive trading days ending on the trading day before the date in question.

         (b) As used in this  Section 3.7, the term closing bid price shall mean
(i) the  closing  bid price  thereof on any such  trading  date,  as reported by
Bloomberg,  L.P. or (ii) in the event the Common Shares are not reported on such
system,  the fair market value of the Common Stock as determined by the Board of
Directors of the Company in its good faith judgment.

ARTICLE 4.        MERGERS.

         The Company  shall not  consolidate  or merge into,  or transfer all or
substantially  all of its assets to, any person,  unless such person assumes the
obligations  of the Company  under this  Debenture  and  immediately  after such
transaction  no Event of Default  exists.  Any  reference  herein to the Company
shall refer to such surviving or transferee  corporation  and the obligations of
the Company  shall  terminate  upon such  assumption.  If the Company  merges or
consolidates with another corporation or sells or transfers all or substantially
all of its assets to another person and the holders of the

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Common Shares are entitled to receive  stock,  securities or property in respect
of or in  exchange  for  Common  Shares,  then as a  condition  of such  merger,
consolidation,  sale or transfer, either (i) the Company and any such successor,
purchaser  or  transferee  shall  amend this  Debenture  to provide  that it may
thereafter  be  converted on the terms and subject to the  conditions  set forth
above into the kind and amount of stock,  securities or property receivable upon
such merger, consolidation, sale or transfer by a holder of the number of shares
of Common Stock into which this Debenture might have been converted  immediately
before such merger,  consolidation,  sale or transfer, or (ii) if the Company is
not the surviving entity in such merger,  consolidation,  sale or transfer,  the
Company  shall  give the  Holder at least 30 days  prior  written  notice of the
expected closing date of such transaction,  and if any portion of this Debenture
has not been  converted into Common Stock at the election of the Holder prior to
such closing,  then the remaining principal amount of this Debenture may, at the
option of the Purchaser, be converted into shares of Common Stock at the closing
of such  transaction.  The Conversion  Price shall be the same as the applicable
Conversion Price defined in Section 3 above.

ARTICLE 5.        REPORTS.

         The Company  will mail to the Holder  hereof at its address as shown on
the  Register a copy of any annual,  quarterly  or current  report that it files
with the  Securities and Exchange  Commission  promptly after the filing thereof
and a copy of any annual,  quarterly or other report or proxy  statement that it
gives to its shareholders generally at the time such report or statement is sent
to shareholders.

ARTICLE 6.        DEFAULTS AND REMEDIES.

         SECTION 6.1. Events of Default. An "Event of Default" occurs if (a) the
Company does not make the payment of the  principal of this  Debenture  when the
same becomes due and payable at maturity, upon redemption or otherwise,  (b) the
Company does not make a payment of interest when such  interest  becomes due and
payable and such default  continues for a period of 10 days thereafter,  (c) the
Company  fails to issue Common  Shares upon  conversion,  within the time period
specified in Section 3.2, (d) the Company  fails to comply with any of its other
agreements in this  Debenture the Company  ceases to be eligible with respect to
the use of Form S-3 for the filing of a resale  registration  statement with the
Securities and Exchange Commission,  (f) the Company's Common Shares cease to be
quoted on any of the New York  Stock  Exchange,  American  Stock  Exchange,  the
NASDAQ-National Market or NASDAQ-Small Cap for a period in excess of 60 calendar
days, (g) an "Event of Default" occurs in any of the other Debentures  issued in
connection with the Agreement,  (h) the Company  defaults under the terms of any
existing or "funded indebtedness" in excess of $500,000, and such default is not
remedied  within  the  cure  period  associated  therewith,  or (i) the  Company
pursuant  to or  within  the  meaning  of any  Bankruptcy  Law  (as  hereinafter
defined): (a)

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(INTELECT COMMUNICATIONS SYSTEMS LIMITED)





commences a  voluntary  case;  (b)  consents to the entry of an order for relief
against  it in an  involuntary  case;  (c)  consents  to  the  appointment  of a
Custodian (as hereinafter  defined) of it or for all or substantially all of its
property;  (d) makes a general  assignment for the benefit of its creditors;  or
(e) a court of  competent  jurisdiction  enters  an order or  decree  under  any
Bankruptcy  Law that:  (A) is for relief  against the Company in an  involuntary
case; (B) appoints a Custodian of the Company or for all or substantially all of
its  property or (C) orders the  liquidation  of the  Company,  and the order or
decree remains  unstayed and in effect for 60 days. As used in this Section 6.1,
the term  "Bankruptcy  Law"  means  Title 11 of the  United  States  Code or any
similar Federal or State law for the relief of debtors or such other  applicable
laws. The term "Custodian" means any receiver, trustee, assignee,  liquidator or
similar official under any Bankruptcy Law. The term "funded  indebtedness" means
indebtedness for borrowed money of Seller, indebtedness evidenced by securities,
debentures,  bonds,  notes or other similar  instruments  issued by Seller,  all
obligations  of Seller  issued or  assumed  as the  deferred  purchase  price of
property, all liabilities secured by any lien on any property or asset of Seller
and all  obligations  of the type  referred  to herein of other  persons for the
payment of which  Seller is  responsible  or liable as  obligor,  guarantor,  or
otherwise.

         SECTION  6.2.  ACCELERATION.  If an  Event  of  Default  occurs  and is
continuing,  the  Holder  hereof by  notice  to the  Company,  may  declare  the
principal of and accrued interest on this Debenture to be due and payable.  Upon
such  declaration,  the principal  and interest  hereof shall be due and payable
immediately.

ARTICLE 7.        REGISTERED DEBENTURES.

         SECTION 7.1.  SERIES.  This Debenture is one of two Series B Debentures
issued to the Holder and  Infinity  Investors  Ltd.  pursuant  to the  Agreement
having  an  aggregate  principal  amount  of Five  Million  and  No/100  Dollars
($5,000,000),  which are  identical.  Such  Debentures  are  referred  to herein
collectively as the "Debentures."

         SECTION 7.2. RECORD OWNERSHIP. The Company,  pursuant to the mechanisms
established under the Transfer Agent Agreement, shall maintain a register of the
holders of the Debentures (the "Register") showing their names and addresses and
the serial numbers and principal  amounts of Debentures issues to or transferred
of  record  by them  from  time to  time.  The  Register  may be  maintained  in
electronic,  magnetic  or other  computerized  form.  The  Company may treat the
person  named as the Holder of this  Debenture in the Register as the sole owner
of this  Debenture.  The  registered  Holder  of this  Debenture  is the  person
exclusively entitled to receive payments of interest on this Debenture,  receive
notifications  with respect to this Debenture,  convert it into Common Stock and
otherwise exercise all of the rights and powers as the absolute owner hereof.


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         SECTION 7.3. REGISTRATION OF TRANSFER.  Transfers of this Debenture may
be registered on the books of the Company  maintained for such purpose  pursuant
to Section 7.2 above (i.e.,  the Register).  Transfers  shall be registered when
the Transfer Agent is presented  with a request to register the transfer  hereof
pursuant  to the terms of the  Transfer  Agent  Agreement  and the  Company  has
received  evidence  satisfactory  to it that such  transfer is  rightful  and in
compliance  with all applicable  laws,  including tax laws and State and Federal
securities laws.

ARTICLE 8.        NOTICES.

         Any notice  which is required  by the  Company  under the terms of this
Debentures  shall be duly given if it is in writing and delivered in person,  by
telecopy, by recognized overnight courier or mailed by first class mail, postage
prepaid and directed to the Holder of the Debenture at its address as it appears
on the Register or if to the Company to its  principal  executive  offices.  The
time when such notice is sent shall be the time of the giving of the notice.

         All notices to Holders are to be mailed to:
         -----------------------
         -----------------------
         -----------------------
         -----------------------
         Telephone:
         Fax:

         All notices to the Company are to be mailed to:

         Intelect Communications Systems Limited
         Reid House 31 Church Street
         Hamilton, Bermuda
         Attn:  President
         Telephone:  441/295-8639
         Fax:  441/292-5560

         With copy to:

         Hale and Dorr
         60 State Street
         Boston, Massachusetts 02109
         Telephone:  617/526-6000
         Fax:  617/526-5000
         Attn:  Philip P. Rossetti


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ARTICLE 9.        TIMES.

         Where this Debenture authorizes or requires the payment of money or the
performance  of a condition  or  obligation  on a Saturday or Sunday or a public
holiday,  or authorizes or requires the payment of money or the performance of a
condition or obligation within, before or after a period of time computed from a
certain date, and such period of time ends on a Saturday or a Sunday or a public
holiday,  such payment may be made or condition or  obligation  performed on the
next  succeeding  business day, and if the period ends at a specified hour, such
payment may be made or condition  performed,  at or before the same hour of such
next  succeeding  business  day,  with the same  force and  effect as if made or
performed in accordance with the terms of this Debenture. Where time is extended
by virtue of the  provisions  of this Article 9, such extended time shall not be
included in the computation of interest.

ARTICLE 10.       RULES OF CONSTRUCTION.

         In this Debenture,  unless the context otherwise requires, words in the
singular number include the plural, and in the plural include the singular,  and
words of the masculine gender include the feminine and the neuter,  and when the
sense so  indicates,  words of the neuter  gender may refer to any  gender.  The
numbers and titles of sections  contained  in this  Debenture  are  inserted for
convenience  of reference  only,  and they neither form a part of this Debenture
nor are they to be used in the construction or interpretation hereof.  Wherever,
in this Debenture,  a determination of the Company is required or allowed,  such
determination  shall be made by a  majority  of the  Board of  Directors  of the
Company and if it is made in good faith, it shall be conclusive and binding upon
the Company and the Holder of this Debenture.

ARTICLE 11.       GOVERNING LAW.

         The validity,  terms,  performance  and  enforcement  of this Debenture
shall be governed and construed by the provisions  hereof and in accordance with
the laws of Bermuda.




                            [Signature page follows]


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         IN WITNESS WHEREOF,  the Company has duly executed this Debenture as of
the date first written above.

                                     INTELECT COMMUNICATIONS SYSTEMS
                                     LIMITED



                                     By:
                                        ----------------------------------------
                                     Name     PETER G. LEIGHTON
                                         ---------------------------------------
                                     Title             PRESIDENT
                                          --------------------------------------

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                              NOTICE OF CONVERSION

         [To be completed and signed only upon conversion of Debenture]

         The  undersigned,  the  Holder of this  Debenture,  hereby  irrevocably
elects to exercise  the right to convert it into common  shares,  par value $ 10
per share, of Intelect Communications Systems Limited as follows:

[Complete if less than all                      Dollars ($       )
of principal amount is to          ---------------------------------------------
be converted                       ($10,000 or integral multiples of $10,000)

[Signature must be                 ---------------------------------------------
guaranteed if registered           (Name of Holder of shares if different than
holder of stock differs from       registered Holder of Debenture)
registered Holder of
Debenture)

                                   ---------------------------------------------
                                   (Address of Holder if different than address
                                   of registered Holder of Debenture)


                                   ---------------------------------------------
                                   (Social Security of EIN of Holder of shares
                                   if different than Holder of Debenture)


Date:                              Sign:
     ---------------                     ---------------------------------------
                                         (Signature must conform in all respects
                                         to name of Holder shown on face of this
                                         Debenture)

NOTICE OF CONVERSION