SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549



                                  SCHEDULE 13G
                    UNDER THE SECURITIES EXCHANGE ACT OF 1934
                                (AMENDMENT NO. )

                                 Bel Fuse Cl B
                         ------------------------------
                                (NAME OF ISSUER)

                     CLASS B STOCK, $.10 PAR VALUE PER SHARE
                   -------------------------------------------
                         (TITLE OF CLASS OF SECURITIES)

                                    077347300
                          ----------------------------
                                 (CUSIP NUMBER)

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 the
disclosures provided in a prior cover page.

The information required in 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).


- -------------------------------------------------------------- 1 NAME OF REPORTING PERSONS S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS EQSF ADVISERS, INC. (EIN 13-3354359) - -------------------------------------------------------------- - -------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [ ] - -------------------------------------------------------------- - -------------------------------------------------------------- 3 SEC USE ONLY - -------------------------------------------------------------- - -------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION NEW YORK CORPORATION - -------------------------------------------------------------- - -------------------------------------------------------------- 5 SOLE VOTING POWER 238,700 NUMBER OF --------------------------------------------- --------------------------------------------- SHARES 6 SHARED VOTING POWER BENEFICIALLY OWNED BY --------------------------------------------- --------------------------------------------- EACH 7 SOLE DISPOSITIVE POWER REPORTING PERSON 238,700 --------------------------------------------- --------------------------------------------- WITH 8 SHARED DISPOSITIVE POWER - -------------------------------------------------------------- - -------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 238,700 - -------------------------------------------------------------- - -------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] - -------------------------------------------------------------- - -------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 2.99% - -------------------------------------------------------------- - -------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* IA - -------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT!

- -------------------------------------------------------------- 1 NAME OF REPORTING PERSONS S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS M.J. WHITMAN ADVISERS, INC. (EIN 13-3686379) - -------------------------------------------------------------- - -------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [ ] - -------------------------------------------------------------- - -------------------------------------------------------------- 3 SEC USE ONLY - -------------------------------------------------------------- - -------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION NEW YORK CORPORATION - -------------------------------------------------------------- - -------------------------------------------------------------- 5 SOLE VOTING POWER 115,175 NUMBER OF --------------------------------------------- --------------------------------------------- SHARES 6 SHARED VOTING POWER BENEFICIALLY OWNED BY NONE --------------------------------------------- --------------------------------------------- EACH 7 SOLE DISPOSITIVE POWER REPORTING PERSON 195,175 --------------------------------------------- --------------------------------------------- WITH 8 SHARED DISPOSITIVE POWER NONE - -------------------------------------------------------------- - -------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON 195,175 - -------------------------------------------------------------- - -------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] - -------------------------------------------------------------- - -------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) 2.44% - -------------------------------------------------------------- - -------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* IA - -------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT!

- -------------------------------------------------------------- 1 NAME OF REPORTING PERSONS S.S. OR I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS MARTIN J. WHITMAN - -------------------------------------------------------------- - -------------------------------------------------------------- 2 CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP* (a) [ ] (b) [ ] - -------------------------------------------------------------- - -------------------------------------------------------------- 3 SEC USE ONLY - -------------------------------------------------------------- - -------------------------------------------------------------- 4 CITIZENSHIP OR PLACE OF ORGANIZATION USA - -------------------------------------------------------------- - -------------------------------------------------------------- 5 SOLE VOTING POWER NUMBER OF NONE (SEE ITEM 4) --------------------------------------------- --------------------------------------------- 6 SHARED VOTING POWER SHARES NONE BENEFICIALLY OWNED BY --------------------------------------------- --------------------------------------------- EACH 7 SOLE DISPOSITIVE POWER REPORTING NONE (SEE ITEM 4) --------------------------------------------- --------------------------------------------- PERSON WITH 8 SHARED DISPOSITIVE POWER NONE - -------------------------------------------------------------- - -------------------------------------------------------------- 9 AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON -0- (SEE ITEM 4) - -------------------------------------------------------------- - -------------------------------------------------------------- 10 CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES* [ ] - -------------------------------------------------------------- - -------------------------------------------------------------- 11 PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11) -0- - -------------------------------------------------------------- - -------------------------------------------------------------- 12 TYPE OF REPORTING PERSON* IN - -------------------------------------------------------------- *SEE INSTRUCTIONS BEFORE FILLING OUT! ITEM 1. (A) NAME OF ISSUER: --------------- Bel Fuse Cl B (the "Issuer"). (B) ADDRESS OF ISSUER'S PRINCIPAL EXECUTIVE OFFICES OR, IF NONE, RESIDENCE: ----------------------------------------------------------------------- 198 Van Vorst Street, Jersey City, NJ 07302 ITEM 2. (A) NAME OF PERSON FILING: This schedule is being jointly filed by EQSF Advisers, Inc. ("EQSF"), M.J. Whitman Advisers, Inc. ("MJWA") and Martin J. Whitman, the Chief Executive Officer of EQSF and MJWA and controlling person of EQSF and MJWA. (EQSF, MJWA and Martin J. Whitman are sometimes collectively referred to hereinafter as "Filer"). Attached hereto as an exhibit is a copy of the joint Schedule 13G filing agreement among the reporting persons. (B) ADDRESS OF PRINCIPAL BUSINESS OFFICE: ------------------------------------- The address of the principal executive office of EQSF, MJWA and Mr. Whitman is: 767 Third Avenue, New York, New York 10017-2023. (C) CITIZENSHIP: ------------ The citizenship or place of organization of each of the reporting persons is as follows: EQSF ---- New York State Corporation. MJWA ---- New York State Corporation. MARTIN J. WHITMAN ----------------- United States Citizen. (D) TITLE OF CLASS OF SECURITIES: ----------------------------- Cl B Stock, $.10 par value per share. (E) CUSIP NUMBER: ------------- 077347300 ITEM 3.IF THIS STATEMENT IS BEING FILED PURSUANT TO RULES 13D-1(B), OR 13D-2(B), CHECK WHETHER THE PERSON FILING IS A: (E) Investment Adviser registered under section 203 of the INVESTMENT ADVISERS ACT OF 1940 (EQSF AND MJWA). ITEM 4. OWNERSHIP. (a) & (b)EQSF beneficially owns 238,700 shares, or 2.99% of the class of securities of the issuer. MJWA beneficially owns 195,175 shares, or 2.44% of the class of securities of the issuer. (c) (i) EQSF: 238,700 MJWA: 115,175 (ii) Not applicable. (iii) EQSF: 238,700 MJWA: 195,175 (iv) Not applicable. Mr. Whitman disclaims beneficial ownership of all such shares. ITEM 5. OWNERSHIP OF FIVE PERCENT OR LESS OF A CLASS. Not applicable. ITEM 6. OWNERSHIP OF MORE THAN FIVE PERCENT ON BEHALF OF ANOTHER PERSON. Third Avenue Value Portfolio of the WRL Series Fund, an investment company registered under the Investment Company Act of 1940, has the right to receive dividends from, and the proceeds from the sale of, 39,400 of the shares reported by EQSF, Third Avenue Variable Series Trust of the Third Avenue Variable Portfolio, an investment company registered under the Investment Company Act of 1940, has the right to receive dividends from, and the proceeds from the sale of, 23,600 of the shares reported by EQSF, and Third Avenue Small Cap Value Fund, an investment company registered under the Investment Company Act of 1940, has the right to receive dividends from, and the proceeds from the sale of, 175,700 of the shares reported by EQSF. Various clients for whom MJWA acts as investment advisor have the right to receive dividends from, and the proceeds of the sale of, the shares reported by MJWA. ITEM 7. IDENTIFICATION AND CLASSIFICATION OF THE SUBSIDIARY WHICH ACQUIRED THE SECURITY BEING REPORTED ON BY THE PARENT HOLDING COMPANY. Not Applicable. ITEM 8. IDENTIFICATION AND CLASSIFICATION OF MEMBERS OF THE GROUP. Not applicable. ITEM 9. NOTICE OF DISSOLUTION OF GROUP. Not applicable. ITEM 10. CERTIFICATION. By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired in the ordinary course of business and were not acquired for the purpose of and do not have the effect of changing or influencing the control of the issuer of such securities and were not acquired in connection with or as a participant in any transaction having such purposes or effect.

SIGNATURE After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct. May 10, 2001 -------------------------------- (Date) EQSF ADVISERS, INC. BY:/S/ MARTIN J. WHITMAN ------------------------ Martin J. Whitman Chairman, President and Chief Executive Officer M.J. WHITMAN ADVISERS, INC. BY:/S/ MARTIN J. WHITMAN ---------------------- Martin J. Whitman Chairman and Chief Executive Officer /S/ MARTIN J. WHITMAN ----------------------- Martin J. Whitman, President

                                                                       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 Entities (as such term is defined in the Schedule 13G) on behalf
of each of them of a statement on Schedule 13G  (including  amendments  thereto)
with respect to the Class B Stock,  $.10 par value per share,  of Bel Fuse,  and
that this  Agreement  be  included  as an  Exhibit to such  joint  filing.  This
Agreement  may be  executed  in any number of  counterparts  all of which  taken
together shall constitute one and the same instrument.

         IN WITNESS WHEREOF,  the undersigned hereby execute this Agreement this
10th day of May, 2001.

                                 EQSF ADVISERS, INC.

                                 BY:/S/ MARTIN J. WHITMAN
                                 ------------------------
                                 Martin J. Whitman
                                 Chairman, President and Chief Executive Officer

                                 M.J. WHITMAN ADVISERS, INC.

                                 BY:/S/  MARTIN J. WHITMAN
                                 ----------------------
                                 Martin J. Whitman
                                 Chairman and Chief Executive Officer

                                 /S/  MARTIN J. WHITMAN
                                 ---------------------------
                                 Martin J. Whitman