UNITED STATES
        SECURITIES AND EXCHANGE COMMISSION
              Washington, D.C. 20549

                   SCHEDULE 13D

     Under the Securities Exchange Act of 1934
             (Amendment No.   1    )*

                Telco Systems, Inc.
                 (Name of Issuer)

Common Stock, $.01 Par Value
(Title of Class of Securities)

878904101
                  (CUSIP Number)
                         
Kathleen S. Tillotson, Esq., Kopp Investment Advisors, 7701 France Ave.
                  So., Suite 500
Edina, MN 55435 (612) 841-0400  
(Name, Address and Telephone Number of Person Authorized to Receive
            Notices and Communications)

4/14/98 
(Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of Rule 13d- 1(b)(3) or (4), check the following box [      ].

Check the following box if a fee is being paid with the statement [      ].  (A
fee is not required only if the reporting person: (1) has a previous statement
on file reporting beneficial ownership of more than five percent of the class
of securities described in Item 1; and (2) has filed no amendment subsequent
thereto reporting beneficial ownership of five percent or less of such class. 
(See Rule 13d-7.)  

The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.  

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




                   SCHEDULE 13D

CUSIP No.           878904101                Page 1 of 3

     l) Name of Reporting Person
         S.S. or I.R.S. Identification No. of Person

               Kopp Investment Advisors, Inc.
               I.D. No. 41-1663810

     2) Check the appropriate box if a Member of a Group

         (a)

         (b)   X    

     3) SEC Use Only

     4) Source of Funds

                OO: Client Funds; WC

     5) Check Box if Disclosure of Legal Proceedings is Required
          Pursuant to Items 2(d) or 2(e)     [     ]

     6) Citizenship or Place of Organization

               Minnesota

     Number of shares         7) Sole Voting Power:    645,600 
     Beneficially Owned
     by Each Reporting
     Person With:             8) Shared Voting Power:  0

                         9) Sole Dispositive Power:    200,000

                         10) Shared Dispositive Power:
                                   3,856,564

     11) Aggregate Amount Beneficially Owned by Each Reporting
           Person
                    4,056,564

     12)  Check Box if the Aggregate Amount in Row (11) Excludes           
            Certain Shares*        [    ]

     13)  Percent of Class Represented by Amount in Row (11)

                    36.8%

     14)  Type of Reporting Person IA
                         
                   SCHEDULE 13D

CUSIP No       878904101                Page 2 of 3

     l) Name of Reporting Person
        S.S. or I.R.S. Identification No. of Person

               Kopp Holding Company
               I.D. No. 41-1875362

     2) Check the appropriate box if a Member of a Group

         (a)

         (b)   X

     3) SEC Use Only

     4) Source of Funds

               Not applicable - indirect beneficial ownership

     5) Check Box if Disclosure of Legal Proceedings is Required
          Pursuant to Items 2(d) or 2(e)     [   ]

     6) Citizenship or Place of Organization

               Minnesota

     Number of shares         7) Sole Voting Power:    0 
     Beneficially Owned 
     by Each Reporting
     Person With:             8) Shared Voting Power:  0

                         9) Sole Dispositive Power:    0

                         10) Shared Dispositive Power:  0

     11) Aggregate Amount Beneficially Owned by Each Reporting
           Person

                    4,056,564

     12)  Check Box if the Aggregate Amount in Row (11) Excludes
            Certain Shares*      [  ]

     13)  Percent of Class Represented by Amount in Row (11)

                    36.8%

     14)  Type of Reporting Person HC

                   SCHEDULE 13D

CUSIP No.      878904101                Page 3 of 3

     l) Name of Reporting Person
         S.S. or I.R.S. Identification No. of Person

               LeRoy C. Kopp

     2) Check the appropriate box if a Member of a Group

         (a)

         (b)   X

     3) SEC Use Only

     4) Source of Funds

               PF, OO

     5) Check Box if Disclosure of Legal Proceedings is Required
          Pursuant to Items 2(d) or 2(e)    [  ]

     6) Citizenship or Place of Organization

               United States

     Number of shares         7) Sole Voting Power:    267,000
     Beneficially Owned
     by Each Reporting
     Person With:             8) Shared Voting Power:  0

                         9) Sole Dispositive Power:    267,000

                         10) Shared Dispositive Power:  0

     11) Aggregate Amount Beneficially Owned by Each Reporting
           Person

                    4,323,564

     12)  Check Box if the Aggregate Amount in Row (11) Excludes
            Certain Shares*         [       ]

     13)  Percent of Class Represented by Amount in Row (11)

                    39.2%

     14)  Type of Reporting Person IN


Item 1.  Security and Issuer

     This statement relates to the common stock, $.01 par value per share
("Common Stock"), of Telco Systems, Inc., a Delaware corporation
("Company"), whose principal executive offices are located at 63 Nahatan
Street, Norwood, MA 02062.  The approximate aggregate percentage of
shares of Common Stock reported beneficially owned by each person herein
is based on 11,022,699 shares outstanding, which is the total number of
shares of Common Stock outstanding as of April 9, 1998, as reflected in the
Company's quarterly report on Form 10-Q filed with the Securities and
Exchange Commission on April 16, 1998, for the quarter ended March 1,
1998.  Unless otherwise indicated, the holdings reported herein are as of the
close of business on April 20, 1998.

Item 2.  Identity and Background

     (a) This statement is filed by Kopp Investment Advisors, Inc.
("KIA"), with respect to shares of Common Stock beneficially owned directly
by it and held in discretionary accounts managed by KIA; Kopp Holding
Company ("KHC"), solely as the parent corporation of KIA and indirect
beneficial owner of the shares beneficially owned by KIA; and LeRoy C.
Kopp individually with respect to shares of Common Stock beneficially
owned directly by him and indirectly by him by virtue of his ownership of all
of the stock of KHC.  The foregoing persons are hereinafter sometimes
referred to as "Reporting Persons."  Certain information concerning the
directors and executive officers of the corporate Reporting Persons is set forth
on Schedule A attached hereto and incorporated herein by reference.  Any
disclosures with respect to persons other than the Reporting Persons are made
on information and belief after making inquiry to the appropriate party.

     (b) The business address of each of the Reporting Persons and
directors and executive officers is 7701 France Avenue South, Suite 500,
Edina, MN 55435.

     ( c) The principal business of KIA is that of an investment advisor
managing discretionary accounts owned by numerous third-party clients,
including the Kopp Emerging Growth Fund, a registered investment company
incorporated under Minnesota law.  KHC is a holding company engaged,
through subsidiaries, in the investment industry.  The principal occupation of
Mr. Kopp is serving as the president of KHC and KIA.

     (d) None of the persons referred to in paragraph (a) above has, during
the last five years, been convicted in a criminal proceeding (excluding traffic
violations and/or similar misdemeanors).

     (e)  None of the persons referred to in paragraph (a) above has, during
the last five years, been a party to a civil proceeding of a judicial or
administrative body of competent jurisdiction and as a result of such
proceeding was or is subject to a judgment, decree, or final order enjoining
future violations of, or prohibiting or mandating activities subject to, federal
or state securities laws or finding any violation with respect to such laws.

     (f)  KIA and KHC are Minnesota corporations.  Mr. Kopp and all
other directors and executive officers of the Reporting Persons are citizens of
the United States.

Item 3.  Source and Amount of Funds or Other Consideration

     The net investment cost (including commissions, if any) of the shares
of Common Stock directly or indirectly beneficially owned by Mr. Kopp,
which includes shares beneficially owned by the other Reporting Persons, at
April 20, 1998, was $46,305,639.13.  The shares beneficially owned by KIA
were purchased with the investment capital of KIA or the investment capital
of the owners of the discretionary accounts.  The shares beneficially owned
directly by Mr. Kopp were purchased with his investment capital or the funds
of an employee benefit plan or 501(c)(3) corporation.  See Item 5 below.

Item 4.  Purpose of Transaction

     The Reporting Persons acquired the shares of Common Stock for
investment purposes, and the Reporting Persons intend to evaluate the
performance of such securities as an investment in the ordinary course of
business.  The Reporting Persons pursue an investment objective of long term
capital appreciation.  In pursuing this investment objective, the Reporting
Persons analyze the management, operations  and markets of companies in
which they invest, including the Company, on a continual basis through
analysis of research and discussions with industry and market observers and
with representatives of such companies.

     Each Reporting Person that owns shares of Common Stock assesses
the Company's business, financial condition, and results of operations as well
as economic conditions and securities markets in general and those for the
Company's shares in particular.  Depending on such assessments, one or
more of such Reporting Persons may acquire additional shares or may sell or
otherwise dispose of all or some of the shares of Common Stock.  Such
actions will depend on a variety of factors, including current and anticipated
trading prices for the Common Stock, alternative investment opportunities,
and general economic, financial market, and industry conditions.

     The Reporting Persons understand that prior purchases of shares of
Common Stock, if any, by persons named in Schedule A to this statement
were made for the purpose of each such person's personal investment.

     Except as described in this Item 4, none of the Reporting Persons nor
any other person named in Schedule A has any plans or proposals that relate
to, or would result in, any matter required to be disclosed in response to
paragraphs (a) through (j), inclusive, of Item 4 of Schedule 13D.

Item 5.  Interest in Securities of the Issuer

     (a) Through its own investment account, KIA is the direct owner of
200,000 shares, or 1.8%, of the Common Stock.  By virtue of limited powers
of attorney and/or investment advisory agreements, KIA is the beneficial
owner of an additional 3,856,564 shares, or 35%, of the Common Stock. KIA
has sole voting power over its investment account and, by special agreement,
over a small percentage of the shares managed for clients.  Under its standard
investment agreement, KIA does not vote its clients' shares.  By virtue of the
relationships described in Item 2 of this statement, KHC and Mr. Kopp have
indirect beneficial ownership of the shares beneficially owned by KIA.
     
     Mr. Kopp's direct beneficial ownership comprises Common Stock
held in the Kopp Holding Company Profit Sharing Plan ("Plan"), for which
he serves as sole trustee; held in the Kopp Family Foundation ("KFF"), for
which he serves as a director; held in the LeRoy C. Kopp Individual
Retirement Account ("IRA"); and held directly by him.  The Plan is the direct
owner of 7,000 shares, or less than .1%, of the Common Stock.  The KFF is
the direct owner of 30,000 shares, or .3%, of the Common Stock.  The IRA is
the direct owner of 130,000 shares, or 1.2%, of the Common Stock.  Mr.
Kopp owns directly 100,000 shares, or .9%, of the Common Stock.  In the
aggregate, including the shares beneficially owned by KIA, Mr. Kopp may be
deemed beneficially to own a total of 4,323,564 shares, or 39.2%, of the
Common Stock.

     (b) KIA has sole power to vote 645,600 shares of the Common Stock. 
KIA has sole power to dispose of 200,000 shares, which are held in its
investment account.  Pursuant to the limited powers of attorney granted to
KIA by its clients, which generally are terminable immediately upon notice,
KIA in effect shares with the majority of its clients the power to dispose of
the Common Stock owned by them.  In effect Mr. Kopp has sole power to
dispose of and to vote the Common Stock beneficially owned directly by
him.

     ( c) The identity of the Reporting Person, type of transaction, date,
number of shares, and price per share (excluding commission) for all
transactions in the Common Stock by the Reporting Persons within the past
60 days are set forth on Schedule B attached hereto and incorporated by
reference herein.  Substantially all trades by the Reporting Persons are done
in the over-the-counter market.

     (d) With the exception of the clients of KIA and the employees of
KHC, no person other than each respective record owner of shares of
Common Stock is known to have the right to receive or the power to direct
the receipt of dividends from or the proceeds of the sale of such shares of
Common Stock.

     (e) Not applicable.

Item 6.  Contracts, Arrangements, Understandings or Relationships with
Respect to Securities of the Issuer

     Except as otherwise expressly disclosed herein, there are no contracts,
arrangements, understandings, or relationships (legal or otherwise) among the
persons named in Item 2 hereof or between such persons and any other
person with respect to the Common Stock.

Item 7.  Material to Be Filed as Exhibits

     Exhibit 1 - A written agreement relating to the filing of this statement
pursuant to Rule 13d-1(f).
                    Signatures
                         
     After reasonable inquiry and to the best of our knowledge and belief,
the undersigned certify that the information set forth in this statement is
true, complete, and correct.


Dated:                4/22/98                                

KOPP INVESTMENT ADVISORS, INC.

BY:                                                               

TITLE:            Secretary/Treasurer              

KOPP HOLDING COMPANY

BY:                                                               

TITLE:            Secretary/Treasurer              

LEROY C. KOPP

                                                                     
                     Exhibit 1
                         
              JOINT FILING AGREEMENT

     In accordance with Rule 13d-1(f) under the Securities Exchange Act
of 1934, as amended, the undersigned hereby agree to the joint filing with all
other Reporting Persons (as such term is defined in the Schedule 13D) on
behalf of each of them of a statement on Schedule 13D (including
amendments thereto) with respect to the Common Stock (as defined) and to
the attachment of this agreement to the Schedule 13D as Exhibit 1 thereto. 
IN WITNESS WHEREOF, the undersigned hereby execute this Agreement
this     22nd         day of  April 1998   .


KOPP INVESTMENT ADVISORS, INC.

BY:                                                               

TITLE:            President                               

KOPP HOLDING COMPANY

BY:                                                               

TITLE:            President                               

LEROY C. KOPP

                                                                     























                    Schedule A
                         
List of Directors, Executive Officers, and Control Persons
                         
                         
LeRoy C. Kopp, individually, and as sole director and president of Kopp
Investment Advisors, Inc. and Kopp Holding Company
                         
Donald B. Cornelius as chief financial officer of KIA and KHC
                         
                         
Kopp Investment Advisors - Schedule B					

Daily Trade Report					
"February 20, 1998 thru April 20, 1998"					
					
Trade	Reporting				
Date	Person	Activity	Quantity	Symbol	Price

04-20-98	KIA	SELL	1000	telc	10.50
04-20-98	KIA	SELL	1000	telc	10.56
04-17-98	KIA	SELL	1500	telc	10.75
04-16-98	KIA	SELL	500	telc	10.50
04-15-98	KIA	SELL	1000	telc	10.56
04-15-98	KIA	SELL	1500	telc	10.56
04-15-98	KIA	SELL	1000	telc	10.50
04-15-98	KIA	SELL	2500	telc	10.50
04-15-98	KIA	SELL	600	telc	10.50
04-15-98	KIA	SELL	1000	telc	10.50
04-14-98	KIA	SELL	1000	telc	10.50
04-14-98	KIA	SELL	2000	telc	10.50
04-14-98	KIA	SELL	2000	telc	10.50
04-13-98	KIA	SELL	500	telc	10.63
04-09-98	KIA	SELL	1500	telc	10.81
04-09-98	KIA	BUY	1000	telc	11.00
04-09-98	KIA	BUY	1000	telc	10.88
04-09-98	KIA	SELL	2000	telc	10.75
04-08-98	KIA	SELL	1000	telc	10.88
04-08-98	KIA	SELL	1500	telc	10.88
04-08-98	KIA	SELL	2000	telc	10.88
04-03-98	KIA	SELL	1500	telc	11.69
04-01-98	KIA	SELL	700	telc	11.74
03-31-98	KIA	SELL	1200	telc	11.69
03-31-98	KIA	SELL	3000	telc	11.63
03-31-98	KIA	SELL	1000	telc	11.63
03-31-98	KIA	SELL	1000	telc	11.81
03-31-98	KIA	SELL	1000	telc	11.63
03-31-98	KIA	SELL	1000	telc	11.63
03-30-98	KIA	SELL	2000	telc	11.50
03-30-98	KIA	BUY	5000	telc	11.69
03-27-98	KIA	SELL	1000	telc	11.50
03-27-98	KIA	SELL	3000	telc	11.75
03-26-98	KIA	SELL	500	telc	11.00
03-26-98	KIA	BUY	1000	telc	11.38
03-25-98	KIA	SELL	2000	telc	11.38
03-25-98	KIA	SELL	400	telc	11.25
03-25-98	KIA	BUY	100	telc	11.50
03-24-98	KIA	SELL	591	telc	10.06
03-24-98	KIA	SELL	1500	telc	10.31
03-23-98	KIA	SELL	500	telc	10.18
03-23-98	KIA	SELL	1140	telc	10.31
03-20-98	KIA	SELL	1500	telc	10.38
03-20-98	KIA	SELL	2500	telc	10.50
03-20-98	KIA	SELL	8000	telc	10.50
03-19-98	KIA	SELL	3000	telc	10.69
03-19-98	KIA	SELL	500	telc	10.75
03-18-98	KIA	SELL	1000	telc	10.38
03-18-98	KIA	SELL	500	telc	10.69
03-18-98	KIA	SELL	400	telc	10.75
03-17-98	KIA	SELL	1909	telc	10.25
03-17-98	KIA	SELL	600	telc	10.25
03-16-98	KIA	SELL	1200	telc	9.50
03-16-98	KIA	SELL	1200	telc	9.50
03-16-98	KIA	SELL	800	telc	9.50
03-12-98	KIA	SELL	2500	telc	9.50
03-12-98	KIA	SELL	500	telc	9.62
03-11-98	KIA	SELL	1000	telc	9.63
03-10-98	KIA	SELL	1500	telc	9.79
03-10-98	KIA	SELL	1000	telc	9.75
03-09-98	KIA	SELL	3860	telc	9.81
03-09-98	KIA	SELL	1500	telc	9.88
03-09-98	KIA	SELL	2000	telc	9.88
03-06-98	KIA	SELL	500	telc	10.13
03-06-98	KIA	SELL	5000	telc	10.03
03-06-98	KIA	SELL	2500	telc	10.13
03-05-98	KIA	SELL	500	telc	10.00
03-04-98	KIA	SELL	500	telc	10.38
03-02-98	KIA	SELL	300	telc	11.25
03-02-98	KIA	SELL	2000	telc	11.37
02-27-98	KIA	BUY	10000	telc	11.88
02-24-98	KIA	BUY	5100	telc	12.19
02-23-98	KIA	BUY	5000	telc	12.50
02-23-98	KIA	BUY	12500	telc	12.22
02-20-98	KIA	SELL	200	telc	11.75
02-20-98	KIA	BUY	5000	telc	11.94
02-20-98	KIA	SELL	2000	telc	12.06