Product Search

    SEARCH NOW FOR ALL YOUR RADWELL SOLUTIONS

    Radwell is here to supply you with all your plant floor needs.

    Transformers / Audio Transformer

    Radwell is not an authorised distributor, reseller or representative of the products featured on this website. All product names, trademarks, brands and logos used on this site are the property of their respective owners. The depiction, description or sale of products featuring these names, trademarks, brands and logos is for identification purposes only and is not intended to indicate any affiliation with or authorisation by any rights holder.

    Rockwell Disclaimer: The product is used surplus. Radwell is not an authorised surplus dealer or affiliate for the Manufacturer of this product. The product may have older date codes or be an older series than that available direct from the factory or authorised dealers. Because Radwell is not an authorised distributor of this product, the Original Manufacturer’s warranty does not apply. While many Allen-Bradley PLC products will have firmware already installed, Radwell makes no representation as to whether a PLC product will or will not have firmware and, if it does have firmware, whether the firmware is the revision level that you need for your application. Radwell also makes no representations as to your ability or right to download or otherwise obtain firmware for the product from Rockwell, its distributors, or any other source. Radwell also makes no representations as to your right to install any such firmware on the product. Radwell will not obtain or supply firmware on your behalf. It is your obligation to comply with the terms of any End-User License Agreement or similar document related to obtaining or installing firmware.

    Filter Results
    Results 101-150 of 494.
    TRIAD MAGNETICS TY-311P

    TRIAD MAGNETICS

    TY-311P

    AUDIO TRANSFORMER; TURNS RATIO:1:1; PRIMARY IMPEDANCE:600OHM; SECONDARY IMPEDANCE:600OHM; SECONDARY POWER:-; FREQUENCY MAX:3.5KHZ; ISOLATION VOLTAGE:1.5KV; TRANSFORMER APPLICATIONS:DATA/VOIC ...
    £4.02 Price with VAT: £4.82 Buy Surplus As Low As £2.41 Price with VAT: £2.89
    £2.41 Price with VAT: £2.89
    MURATA MANUFACTURING DA101MC-R

    MURATA MANUFACTURING

    MURATA POWER SOLUTIONS

    DA101MC-R

    (PRICE/TC), DIGITAL AUDIO DATA TRANSMISSION TRANSFORMER, TURNS RATIO:1:1, PRIMARY IMPEDANCE:-, SECONDARY IMPEDANCE:-, SECONDARY POWER:-, FREQUENCY MAX:-, ISOLATION VOLTAGE:2KV, TRANSFORMER A ...
    £2.33 Price with VAT: £2.80 Buy Surplus As Low As £1.40 Price with VAT: £1.68
    £1.40 Price with VAT: £1.68
    TRIAD MAGNETICS SP-49

    TRIAD MAGNETICS

    SP-49

    AUDIO TRANSFORMER; TURNS RATIO:1:1.42; PRIMARY IMPEDANCE:300OHM; SECONDARY IMPEDANCE:600OHM; SECONDARY POWER:50MW; FREQUENCY MAX:100KHZ; ISOLATION VOLTAGE:1KV; TRANSFORMER APPLICATIONS:HIGH ...
    £16.55 Price with VAT: £19.86 Buy Surplus As Low As £9.93 Price with VAT: £11.92
    £9.93 Price with VAT: £11.92
    OEP A262A2E

    OEP

    A262A2E

    TRANSFORMER, AUDIO, 1+1:2+2, 150CT/600CT; TURNS RATIO:1:2; PRIMARY IMPEDANCE:150OHM; SECONDARY IMPEDANCE:600OHM; SECONDARY POWER:100MW; FREQUENCY MAX:35KHZ; ISOLATION VOLTAGE:1KV; DC RESISTA ...
    £20.61 Price with VAT: £24.73 Buy Surplus As Low As £12.98 Price with VAT: £15.57
    £12.98 Price with VAT: £15.57
    OEP OEP1200

    OEP

    OEP1200

    TRANSFORMER, ISOLATION, 600/600, OHM; INDUCTANCE:-; PRODUCT RANGE:-; SVHC:NO SVHC (15-JAN-2019); APPROVAL BODIES:BABT, BS, EN; EXTERNAL DEPTH:18MM; EXTERNAL LENGTH / HEIGHT:12.7MM; EXTERNAL ...
    £5.01 Price with VAT: £6.01 Buy Surplus As Low As £3.01 Price with VAT: £3.61
    £3.01 Price with VAT: £3.61
    SAUER SUNDSTRAND R7232A1028

    SAUER SUNDSTRAND

    R7232A1028

    DISCONTINUED BY MANUFACTURER, REMOTE AMPLIFIER, 12 VDC TERMINAL BLOCK
    Buy Surplus As Low As £3,173.88 Price with VAT: £3,808.66
    £3,173.88 Price with VAT: £3,808.66
    Repair Yours £2,634.32 Price with VAT: £3,161.19
    HAMMOND MANUFACTURING 126B

    HAMMOND MANUFACTURING

    126B

    (PRICE/EA) TRANSFORMER - TUBE DRIVER; INTERSTAGE
    £129.98 Price with VAT: £155.97 Buy Surplus As Low As £78.59 Price with VAT: £94.31
    £78.59 Price with VAT: £94.31
    HAMMOND MANUFACTURING 813

    HAMMOND MANUFACTURING

    813

    AUDIO TRANSFORMER ROHS COMPLIANT: YES
    £135.27 Price with VAT: £162.32 Buy Surplus As Low As £81.61 Price with VAT: £97.94
    £81.61 Price with VAT: £97.94
    HAMMOND MANUFACTURING 835

    HAMMOND MANUFACTURING

    835

    AUDIO TRANSFORMER ROHS COMPLIANT: YES
    £169.27 Price with VAT: £203.13 Buy Surplus As Low As £102.02 Price with VAT: £122.42
    £102.02 Price with VAT: £122.42
    HAMMOND MANUFACTURING 844

    HAMMOND MANUFACTURING

    844

    AUDIO TRANSFORMER ROHS COMPLIANT: YES
    £130.73 Price with VAT: £156.88 Buy Surplus As Low As £78.59 Price with VAT: £94.31
    £78.59 Price with VAT: £94.31
    TRIAD MAGNETICS SP-20

    TRIAD MAGNETICS

    SP-20

    TRANSFORMER, 2.88:1, 10K/1.2K; TURNS RATIO:2.88:1; PRIMARY IMPEDANCE:10KOHM; SECONDARY IMPEDANCE:1.2KOHM; SECONDARY POWER:50MW; FREQUENCY MAX:100KHZ; ISOLATION VOLTAGE:1KV; TRANSFORMER APPLI ...
    £11.77 Price with VAT: £14.13 Buy Surplus As Low As £7.07 Price with VAT: £8.48
    £7.07 Price with VAT: £8.48
    OEP A262A3E

    OEP

    A262A3E

    TRANSFORMER,AUDIO,1+1:6.45+6.45,600/250K; TURNS RATIO:1:6.45; PRIMARY IMPEDANCE:150OHM; SECONDARY IMPEDANCE:6.25KOHM; SECONDARY POWER:100MW; FREQUENCY MAX:35KHZ; ISOLATION VOLTAGE:1KV; DC RE ...
    £21.91 Price with VAT: £26.30 Buy Surplus As Low As £13.60 Price with VAT: £16.32
    £13.60 Price with VAT: £16.32
    OEP PT6

    OEP

    PT6

    PULSE TRANSFORMER, 1:1+1, 8 H, 1.4 OHM, 2.8 KV ROHS COMPLIANT: YES
    £5.22 Price with VAT: £6.27 Buy Surplus As Low As £3.13 Price with VAT: £3.76
    £3.13 Price with VAT: £3.76
    OEP TF048

    OEP

    TF048

    LINE ISOLATION TRANSFORMERS; PCB TRANSFORMER TYPE:ENCAPSULATED SAFETY ISOLATING; SECONDARY VOLTAGES:-; POWER RATING:-; FREQUENCY RANGE:-; WINDING TYPE:-; CURRENT RATING:-; ISOLATION VOLTAGE: ...
    £8.31 Price with VAT: £9.98 Buy Surplus As Low As £4.99 Price with VAT: £5.99
    £4.99 Price with VAT: £5.99
    HAMMOND MANUFACTURING 560G

    HAMMOND MANUFACTURING

    560G

    AUDIO TRANSFORMER, 150/600 OHM / 150/600 OHM; TURNS RATIO:1:1; PRIMARY IMPEDANCE:600OHM; SECONDARY IMPEDANCE:600OHM; SECONDARY POWER:-; FREQUENCY MAX:30KHZ; ISOLATION VOLTAGE:500V; DC RESIST ...
    £80.86 Price with VAT: £97.03 Buy Surplus As Low As £49.12 Price with VAT: £58.94
    £49.12 Price with VAT: £58.94
    HAMMOND MANUFACTURING 140Q

    HAMMOND MANUFACTURING

    140Q

    AUDIO TRANSFORMER ;ROHS COMPLIANT: YES
    £85.66 Price with VAT: £102.80 Buy Surplus As Low As £51.39 Price with VAT: £61.67
    £51.39 Price with VAT: £61.67
    HAMMOND MANUFACTURING 141B

    HAMMOND MANUFACTURING

    141B

    AUDIO TRANSFORMER ROHS COMPLIANT: YES
    £35.52 Price with VAT: £42.62 Buy Surplus As Low As £21.91 Price with VAT: £26.30
    £21.91 Price with VAT: £26.30
    HAMMOND MANUFACTURING 850GA

    HAMMOND MANUFACTURING

    850GA

    (PRICE/EA) TRANSFORMER - AUDIO, BROADCAST QUALITY, SEALED
    £168.52 Price with VAT: £202.22 Buy Surplus As Low As £101.26 Price with VAT: £121.51
    £101.26 Price with VAT: £121.51
    HAMMOND MANUFACTURING 850NA

    HAMMOND MANUFACTURING

    850NA

    (PRICE/EA) TRANSFORMER - AUDIO, BROADCAST QUALITY, SEALED
    £168.52 Price with VAT: £202.22 Buy Surplus As Low As £101.26 Price with VAT: £121.51
    £101.26 Price with VAT: £121.51
    HAMMOND MANUFACTURING 107B

    HAMMOND MANUFACTURING

    107B

    (PRICE/EA) AUDIO TRANSFORMER ;ROHS COMPLIANT: NO
    £61.21 Price with VAT: £73.45 Buy Surplus As Low As £37.03 Price with VAT: £44.43
    £37.03 Price with VAT: £44.43
    HAMMOND MANUFACTURING 148Y

    HAMMOND MANUFACTURING

    148Y

    AUDIO TRANSFORMER ROHS COMPLIANT: YES
    £29.47 Price with VAT: £35.37 Buy Surplus As Low As £18.14 Price with VAT: £21.76
    £18.14 Price with VAT: £21.76
    HAMMOND MANUFACTURING 1750A

    HAMMOND MANUFACTURING

    1750A

    (PRICE/EA) TRANSFORMER - TUBE GUITAR AMP - OUTPUT
    £92.95 Price with VAT: £111.54 Buy Surplus As Low As £44.59 Price with VAT: £53.50
    £44.59 Price with VAT: £53.50
    HAMMOND MANUFACTURING 1750B

    HAMMOND MANUFACTURING

    1750B

    (PRICE/EA) TRANSFORMER - TUBE GUITAR AMP - OUTPUT
    £179.10 Price with VAT: £214.92 Buy Surplus As Low As £108.06 Price with VAT: £129.68
    £108.06 Price with VAT: £129.68
    HAMMOND MANUFACTURING 1750C

    HAMMOND MANUFACTURING

    1750C

    (PRICE/EA) TRANSFORMER - TUBE GUITAR AMP - OUTPUT
    £173.05 Price with VAT: £207.66 Buy Surplus As Low As £83.88 Price with VAT: £100.66
    £83.88 Price with VAT: £100.66
    HAMMOND MANUFACTURING 1750J

    HAMMOND MANUFACTURING

    1750J

    (PRICE/EA) TRANSFORMER - TUBE GUITAR AMP - OUTPUT
    £252.40 Price with VAT: £302.88 Buy Surplus As Low As £151.89 Price with VAT: £182.27
    £151.89 Price with VAT: £182.27
    HAMMOND MANUFACTURING 1750JA

    HAMMOND MANUFACTURING

    1750JA

    AUDIO TRANSFORMER, 70HZ TO 15KHZ, 8OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:4.25KOHM; SECONDARY IMPEDANCE:8OHM; SECONDARY POWER:40W; FREQUENCY MAX:15KHZ; ISOLATION VOLTAGE:2KV; TRANSFORMER APPL ...
    £89.17 Price with VAT: £107.01 Buy Surplus As Low As £53.65 Price with VAT: £64.38
    £53.65 Price with VAT: £64.38
    HAMMOND MANUFACTURING 1750K

    HAMMOND MANUFACTURING

    1750K

    (PRICE/EA) TRANSFORMER - TUBE GUITAR AMP - OUTPUT
    £254.67 Price with VAT: £305.60 Buy Surplus As Low As £153.40 Price with VAT: £184.09
    £153.40 Price with VAT: £184.09
    HAMMOND MANUFACTURING 1750KA

    HAMMOND MANUFACTURING

    1750KA

    (PRICE/EA) TRANSFORMER - TUBE GUITAR AMP - OUTPUT
    £254.67 Price with VAT: £305.60 Buy Surplus As Low As £153.40 Price with VAT: £184.09
    £153.40 Price with VAT: £184.09
    HAMMOND MANUFACTURING 1750P

    HAMMOND MANUFACTURING

    1750P

    AUDIO TRANSFORMER, 50HZ TO 12KHZ, 16OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:3.4KOHM; SECONDARY IMPEDANCE:16OHM; SECONDARY POWER:50W; FREQUENCY MAX:12KHZ; ISOLATION VOLTAGE:2.25KV; TRANSFORMER ...
    £130.73 Price with VAT: £156.88 Buy Surplus As Low As £78.59 Price with VAT: £94.31
    £78.59 Price with VAT: £94.31
    HAMMOND MANUFACTURING 107T

    HAMMOND MANUFACTURING

    107T

    (PRICE/EA) AUDIO TRANSFORMER ;ROHS COMPLIANT: YES
    £29.47 Price with VAT: £35.37 Buy Surplus As Low As £18.14 Price with VAT: £21.76
    £18.14 Price with VAT: £21.76
    HAMMOND MANUFACTURING 1750D

    HAMMOND MANUFACTURING

    1750D

    AUDIO TRANSFORMER, 70HZ TO 15KHZ, 16OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:2.35KOHM; SECONDARY IMPEDANCE:16OHM; SECONDARY POWER:100W; FREQUENCY MAX:15KHZ; ISOLATION VOLTAGE:2KV; TRANSFORMER A ...
    £131.49 Price with VAT: £157.79 Buy Surplus As Low As £79.35 Price with VAT: £95.22
    £79.35 Price with VAT: £95.22
    HAMMOND MANUFACTURING 1750F

    HAMMOND MANUFACTURING

    1750F

    (PRICE/EA) TRANSFORMER - TUBE GUITAR AMP - OUTPUT
    £193.46 Price with VAT: £232.15 Buy Surplus As Low As £116.38 Price with VAT: £139.65
    £116.38 Price with VAT: £139.65
    HAMMOND MANUFACTURING 1750G

    HAMMOND MANUFACTURING

    1750G

    AUDIO TRANSFORMER, 50HZ TO 12KHZ, 16OHM; TURNS RATIO:14.21:1; PRIMARY IMPEDANCE:3.8KOHM; SECONDARY IMPEDANCE:16OHM; SECONDARY POWER:50W; FREQUENCY MAX:12KHZ; ISOLATION VOLTAGE:-; TRANSFORMER ...
    £190.43 Price with VAT: £228.52 Buy Surplus As Low As £114.86 Price with VAT: £137.84
    £114.86 Price with VAT: £137.84
    HAMMOND MANUFACTURING 1750H

    HAMMOND MANUFACTURING

    1750H

    AUDIO TRANSFORMER, 70HZ TO 15KHZ, 8OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:6.6KOHM; SECONDARY IMPEDANCE:8OHM; SECONDARY POWER:20W; FREQUENCY MAX:15KHZ; ISOLATION VOLTAGE:1.5KV; TRANSFORMER APP ...
    £64.23 Price with VAT: £77.08 Buy Surplus As Low As £38.54 Price with VAT: £46.25
    £38.54 Price with VAT: £46.25
    HAMMOND MANUFACTURING 1750L

    HAMMOND MANUFACTURING

    1750L

    (PRICE/EA) TRANSFORMER - TUBE GUITAR AMP - OUTPUT
    £249.38 Price with VAT: £299.25 Buy Surplus As Low As £149.63 Price with VAT: £179.55
    £149.63 Price with VAT: £179.55
    HAMMOND MANUFACTURING 1750M

    HAMMOND MANUFACTURING

    1750M

    (PRICE/EA) TRANSFORMER - TUBE GUITAR AMP - OUTPUT
    £254.67 Price with VAT: £305.60 Buy Surplus As Low As £123.18 Price with VAT: £147.81
    £123.18 Price with VAT: £147.81
    HAMMOND MANUFACTURING 1750N

    HAMMOND MANUFACTURING

    1750N

    AUDIO TRANSFORMER, 50HZ TO 15KHZ, 16OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:3.2KOHM; SECONDARY IMPEDANCE:16OHM; SECONDARY POWER:50W; FREQUENCY MAX:15KHZ; ISOLATION VOLTAGE:1.5KV; TRANSFORMER A ...
    £129.98 Price with VAT: £155.97 Buy Surplus As Low As £78.59 Price with VAT: £94.31
    £78.59 Price with VAT: £94.31
    HAMMOND MANUFACTURING 1750NA

    HAMMOND MANUFACTURING

    1750NA

    (PRICE/EA) TRANSFORMER - TUBE GUITAR AMP - OUTPUT
    £224.44 Price with VAT: £269.33 Buy Surplus As Low As £135.27 Price with VAT: £162.32
    £135.27 Price with VAT: £162.32
    HAMMOND MANUFACTURING 1750U

    HAMMOND MANUFACTURING

    1750U

    AUDIO TRANSFORMER, 50HZ TO 12KHZ, 16OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:1.7KOHM; SECONDARY IMPEDANCE:16OHM; SECONDARY POWER:100W; FREQUENCY MAX:12KHZ; ISOLATION VOLTAGE:2.16KV; TRANSFORMER ...
    £157.18 Price with VAT: £188.62 Buy Surplus As Low As £94.46 Price with VAT: £113.35
    £94.46 Price with VAT: £113.35
    HAMMOND MANUFACTURING 1750V

    HAMMOND MANUFACTURING

    1750V

    AUDIO TRANSFORMER, 70HZ TO 15KHZ, 16OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:4KOHM; SECONDARY IMPEDANCE:16OHM; SECONDARY POWER:30W; FREQUENCY MAX:15KHZ; ISOLATION VOLTAGE:2KV; TRANSFORMER APPLI ...
    £157.18 Price with VAT: £188.62 Buy Surplus As Low As £94.46 Price with VAT: £113.35
    £94.46 Price with VAT: £113.35
    HAMMOND MANUFACTURING 1750W

    HAMMOND MANUFACTURING

    1750W

    AUDIO TRANSFORMER, 70HZ TO 15KHZ, 4OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:2KOHM; SECONDARY IMPEDANCE:4OHM; SECONDARY POWER:100W; FREQUENCY MAX:15KHZ; ISOLATION VOLTAGE:2KV; TRANSFORMER APPLIC ...
    £130.73 Price with VAT: £156.88 Buy Surplus As Low As £78.59 Price with VAT: £94.31
    £78.59 Price with VAT: £94.31
    HAMMOND MANUFACTURING 1750X

    HAMMOND MANUFACTURING

    1750X

    AUDIO TRANSFORMER, CHASSIS; TURNS RATIO:-; PRIMARY IMPEDANCE:1.7KOHM; SECONDARY IMPEDANCE:16OHM; SECONDARY POWER:100W; FREQUENCY MAX:12KHZ; ISOLATION VOLTAGE:2.5KV; TRANSFORMER APPLICATIONS: ...
    £168.52 Price with VAT: £202.22 Buy Surplus As Low As £101.26 Price with VAT: £121.51
    £101.26 Price with VAT: £121.51
    HAMMOND MANUFACTURING 1760J

    HAMMOND MANUFACTURING

    1760J

    AUDIO TRANSFORMER, 70HZ TO 15KHZ, 16OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:4KOHM; SECONDARY IMPEDANCE:16OHM; SECONDARY POWER:40W; FREQUENCY MAX:15KHZ; ISOLATION VOLTAGE:1.5KV; TRANSFORMER APP ...
    £81.61 Price with VAT: £97.94 Buy Surplus As Low As £49.12 Price with VAT: £58.94
    £49.12 Price with VAT: £58.94
    HAMMOND MANUFACTURING 1615A

    HAMMOND MANUFACTURING

    1615A

    (PRICE/EA) PUSH-PULL AUDIOPHILE TUBE OUTPUT TRANSFORMER
    £145.09 Price with VAT: £174.11 Buy Surplus As Low As £87.66 Price with VAT: £105.19
    £87.66 Price with VAT: £105.19
    HAMMOND MANUFACTURING 1650H

    HAMMOND MANUFACTURING

    1650H

    (PRICE/EA) TRANSFORMERAUDIO OUTPUT ;ROHS COMPLIANT: YES
    £176.83 Price with VAT: £212.20 Buy Surplus As Low As £106.55 Price with VAT: £127.86
    £106.55 Price with VAT: £127.86
    HAMMOND MANUFACTURING 1650HA

    HAMMOND MANUFACTURING

    1650HA

    (PRICE/EA) PUSH-PULL AUDIOPHILE TUBE OUTPUT TRANSFORMER
    £188.17 Price with VAT: £225.80 Buy Surplus As Low As £113.35 Price with VAT: £136.02
    £113.35 Price with VAT: £136.02
    HAMMOND MANUFACTURING 1650KA

    HAMMOND MANUFACTURING

    1650KA

    (PRICE/EA) PUSH-PULL AUDIOPHILE TUBE OUTPUT TRANSFORMER
    £201.01 Price with VAT: £241.22 Buy Surplus As Low As £120.91 Price with VAT: £145.09
    £120.91 Price with VAT: £145.09
    HAMMOND MANUFACTURING 1750Q

    HAMMOND MANUFACTURING

    1750Q

    AUDIO TRANSFORMER, 70HZ TO 15KHZ, 16OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:7.371KOHM; SECONDARY IMPEDANCE:16OHM; SECONDARY POWER:50W; FREQUENCY MAX:15KHZ; ISOLATION VOLTAGE:2.5KV; TRANSFORMER ...
    £137.53 Price with VAT: £165.04 Buy Surplus As Low As £83.13 Price with VAT: £99.75
    £83.13 Price with VAT: £99.75
    HAMMOND MANUFACTURING 1750R

    HAMMOND MANUFACTURING

    1750R

    AUDIO TRANSFORMER, 11.1:1, 2K/4 OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:2KOHM; SECONDARY IMPEDANCE:16OHM; SECONDARY POWER:100W; FREQUENCY MAX:-; ISOLATION VOLTAGE:2.25KV; TRANSFORMER APPLICATI ...
    £230.48 Price with VAT: £276.58 Buy Surplus As Low As £138.29 Price with VAT: £165.95
    £138.29 Price with VAT: £165.95
    HAMMOND MANUFACTURING 1750T

    HAMMOND MANUFACTURING

    1750T

    AUDIO TRANSFORMER, 70HZ TO 15KHZ, 16OHM; TURNS RATIO:-; PRIMARY IMPEDANCE:4KOHM; SECONDARY IMPEDANCE:16OHM; SECONDARY POWER:30W; FREQUENCY MAX:15KHZ; ISOLATION VOLTAGE:2KV; TRANSFORMER APPLI ...
    £145.09 Price with VAT: £174.11 Buy Surplus As Low As £87.66 Price with VAT: £105.19
    £87.66 Price with VAT: £105.19
    Previous Next
    1 2 3 4 5 6 7 8 9 10
    Related Categories
    Current Transformer Electrical Cable/Wire Enclosure Fuse Isolation Transformer