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Variable Voltage Technology Ltd
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Page Last Updated 02 Mar 2010.
Home Page and Contact Details.
Contents
If none of the above items seem to fit try using Edit/Find(on this page) with suitable words.
All our FAQs are on this one page.
You can scroll or use the link tables scattered through the page.
[1.1] General Pricing Notes
Where do I find the latest price?
Price on web site is the definitive price.
If you call us for a price we look it up on the web!
If a product has a price on a datasheet and a price available from the calculator or the UK price list
you may take the lowest relevant price.
Note that the prices on the datasheet and UK price list have VAT and carriage included.
UK price is in pounds for delivery in UK.
Euro price is in Euro for delivery in Mainland Europe.
You have changed the price since I placed my order. What do I pay?
All orders are fulfilled at the price on the order.
However you may use a web price for up to a month after it changes.
Please add a note on your order to indicate that you are taking advantage of this offer.
If no price was quoted then latest price at the time of payment transaction is used.
You quoted a price different from the website. Why?
This may be because we are preparing an update to the website and have used the new price to quote.
Use the lowest of quoted or website.
Please add a note on your order to indicate that you are taking advantage of this offer.
I want lots of transformers. Can I get a better price?
For larger quantities we can quote a special price.
Please E-mail us.
Note that we cannot accommodate alternative pricing structures on Paypal orders yet.
Back to Menu: Price, Payments and Deliveries
[1.2] Delivery Information
How long do I need to wait for delivery of my order?
We normally carry a small stock of most types.
Stock however may be kept at a partly made level and require varnishing etc.
In some cases we get several orders together for a particular type and have to make to order.
For these reasons you should allow up to four weeks for delivery.
Back to Menu: Price, Payments and Deliveries
How do you send goods?
We use one of the following methods:
- Carrier - Usually DHL for UK.
- For lighter parcels we may use Royal Mail.
- International Carrier - DHL - (We no longer use ParcelForce due to unreliability).
- On Isle of Wight - our own staff will deliver.
- If you are local or visiting the Island - call us for arrangements.
Back to Menu: Price, Payments and Deliveries
What happens during a postal strike?
We use one of the following methods:
- Carrier - DHL for UK.
- International Carrier - DHL.
- On Isle of Wight - our own staff will deliver.
- If you are local or visiting the Island - call us for arrangements.
Back to Menu: Price, Payments and Deliveries
[1.3] Product Price Notes
Why is there a large difference in price between styles?
There is a considerable difference in manufacture cost between different mounting styles.
The reasons are shown below.
U-clamp price is lower than other prices. Why?
All winding wires are connected to tags during winding.
A single clamp with no fixings is used.
Frame mounting is more expensive than U-clamp. Why?
All winding wires are connected to tags during winding.
Two frames are used with studs, nuts etc.
Drop through is more expensive that U-clamp. Why?
Bobbin has to be modified to fit within metal shroud.
Some wires have to be terminated within the winding and additional flying leads fitted.
Studs, nuts etc are required.
Fully Shrouded with Feet is much more expensive than other styles. Why?
Bobbin has to be modified to fit within metal shroud.
All wires have to be terminated within the winding and additional flying leads fitted.
This is very time consuming during winding and test.
Two shrouds are used with studs, nuts etc.
Larger transformers do not seem to have the big difference in price between styles. Why?
Some larger transformers do not have tags fitted on the bobbins.
All wires have to be terminated within the winding and additional flying leads fitted.
This is very time consuming during winding and test.
These are therefore higher priced for all possible variants.
What is the price for a Kit and what do I get?
We have discontinued Kits at present while we set up a new pricing structure for alternative combinations.
Back to Menu: Price, Payments and Deliveries
[1.4] Customer Locations
You have a price calculator but it does not show the product or my location.
This feature is new. Not all data is setup yet.
As product data is added the datasheet price will also change as we altered our price formula in Feb 2005.
Check dates on datasheets to see if this has occurred yet.
If your location is not there yet - Email us and we will add it.
I do not live on the Mainland UK. How much do I pay?
Check below to see if your location is mentioned.
See also our Price Calculator page.
Follow links from Home page.
I live on the Isle of Man. How much do I pay?
Special export prices available. Email for details.
I live on the Channel Isles. How much do I pay?
Special export prices available. Email for details.
I live on the Isle of Wight. How much do I pay?
We are based on the Isle of Wight so can offer reduced carriage charge.
Product can be collected from our factory by arrangement.
I live in the Eurozone part of Europe. How much do I pay?
Prices are in Euros.
Price to retail customers include UK VAT and EU carriage.
Price to VAT registered customers exclude VAT but include EU carriage.
The EU price on the data sheets (where shown) is for VAT registered traders in the Eurozone.
This system will change shortly.
I live in Switzerland. How much do I pay?
Prices are in pound sterling.
Price exclude VAT but include EU carriage.
Email us for details.
I live in the USA. Can you supply me?
We are not able to supply to North America at present for legal reasons.
I live in Canada. Can you supply me?
We are not able to supply to North America at present for legal reasons.
I live in a country you have not listed. Can you supply me?
Email for details or prices.
Back to Menu: Price, Payments and Deliveries
[1.5] Payments
How can I pay?
PayPal/Credit card/Debit card are our preferred methods.
Mastercard. Visa. Switch. Maestro. See 'Payments' page.
Call us and place your order by telephone. Leave a message on Voicemail or Email us and we will call you back.
Use Our On-Line price calculator and order via PayPal.
For details of the PayPal system use PayPal.com or PayPal.co.uk.
DO NOT EMAIL YOUR CREDIT CARD DETAILS. Our site is not secure.
Cheque with order is also acceptable.
When do you bank my cheque or credit card?
We do not normally bank your payment until your transformers are tested.
This is normally a few days before despatch.
However Pay-Pal transactions are passed to the banking system or credit card company within a few days of placing the order.
I need a VAT receipt. How do I get one?
Just ask by Email or Telephone or on your order.
If you have one, put your VAT number on your order or Email it to us before despatch.
We will supply a till receipt or invoice with our VAT number.
Formal order account customers will get a computer generated invoice.
We can E-mail the invoice in HTML format.
Our VAT number is shown on our Home page.
Back to Menu: Price, Payments and Deliveries
[1.6] Product Availability.
Where have some of your products gone?
Some of our Products require special components, materials or processes.
If these are not available or likely to take a long time we will remove affected products from the website.
We may also remove products which are time consuming but infrequently sold to allow a better flow of other products
to satisfy a higher proportion of customers.
What products are affected at present?
What products or changes are you planning to introduce?
- HT, Output and Chokes for Williamson Amplifier - Type testing in progress - First Shipments Spring 2010.
- Mixed product discounting - To be introduced when practical.
Back to Menu: Price, Payments and Deliveries
[2.1] General Technical Notes
How do I get more technical information on a transformer?
General parameters are indicated on the individual data sheets.
Typical default values are shown below.
We hope to upgrade the datasheets gradually.
Back to Menu: Product Technical
[2.2] Mounting style Restrictions
Why are small transformers only available in U-clamp?
For some smaller sizes the only mounting style available is U-clamp.
This is due to our supplier not making frames and shouds for smaller sizes.
Why do large transformers not have U-clamp mounting styles?
For larger sizes the U-clamp is not available.
This is due to a limitation on the mechanical strength of the U-clamps available.
Back to Menu: Product Technical
[2.3] Connections
I have received a transformer but I can't identify the connections.
Wire connections are identified by colour.
Pin numbers are defined by the bobbin manufacturer.
The data sheet (on the website) defines the pin numbers.
Pin numbers are embossed on the bobbin near the pins.
These can be difficult to read, particularly when varnished.
The trick is to alter the lighting of the transformer until the embossing is readable.
We will be adding a page to the website with a diagram of pin positions.
Back to Menu: Product Technical
[2.4] Specifications
Specifications (Push Pull Output Transformers)
Default information unless stated otherwise on data sheet:
- Frequency of operation 40Hz to 18KHz within 3dB No feedback.
- Frequency of operation 20Hz to 20KHz within 6dB. No feedback.
- Tappings are provided at 43% and 20% to allow alternative circuit connections.
Specifications (Single Ended Output Transformers)
Default information unless stated otherwise on data sheet:
- Frequency of operation 40Hz to 18KHz within 3dB No feedback.
- Frequency of operation 20Hz to 20KHz within 6dB. No feedback.
- Transformer is gapped and adjusted for inductance.
- Inductance values (where stated) within 20% of nominal at rated HT current.
Specifications (Mains Transformers)
Default information unless stated otherwise on data sheet:
- Frequency of operation 45Hz to 65Hz.
- Valve HT: Voltages input 10 - 0 - 200 - 220 - 240 RMS.
- Industrial: Voltages input 115 + 115 Series or Parallel.
Specifications (Chokes)
Default information unless stated otherwise on data sheet:
- Inductance values within 20% of nominal at rated current.
- Frequency of operation nominally 45Hz to 130Hz.
- Chokes will perform over a wider range.
- Chokes are designed for smoothing in half wave and full wave mains power supplies.
- HT voltage rating up to 1000 Volts DC.
- Voltage proof from winding to frame is tested at 4000 Volts RMS or equivalent.
- Transient voltage due to load switching up to 2000 Volts Peak.
How do you determinine Output Transformer Impedances?
Secondary Impedances are defined by the Loudspeaker manufacturer.
The impedance value varies by frequency with a resonance at the low frequency end.
Impedance is typically specified at 1kHz.
Typcal common values are:
- 3 ohms.
- 4 ohms
- 7.5 ohms
- 8 ohms
- 15 ohms
- 16 ohms
We have defined a standard set for most of our transformer to cover the range:
- 3 to 4 ohms (we use 3.5 to calculate).
- 7.5 to 8 ohms (we use 7.75 to calculate).
- 15 to 16 ohms (we use 15.5 to calculate).
Primary impedances are determined by a combination of Valve data and Circuit Design.
For Single Ended circuits Valve data usually specifies a suggested impedance load as Ra.
For Push-Pull circuits Valve data usally specifies a suggested impedance load as Raa.
However datasheets and circuit designs are not consistent in this information.
Some say Ra when they mean Raa, some say Ra for one of the two valves.
Valve data often gives a series of alternative impedance figures.
We try and use the most commonly accepted figure by amplifier designers.
The transformers are designed to match impedances on each side.
This is done by matching the square of the turns ratio.
Examples:
- Single ended:
- Ra from data book = 5000 ohms
- Loudspeaker = 3 ohms
- Impedance ratio = 5000 / 3 = 1667
- Turns ratio = sqrt (1667 ) = 41
- Volts ratio = turns ratio
- Push-pull:
- Note that total primary a-a impedance is used.
- Raa from data book = 6000 ohms
- Loudspeaker = 15 ohms
- Impedance ratio = 6000 / 15 = 400
- Turns ratio = sqrt (400 ) = 20
- Volts ratio = turns ratio
- Note:
- For multiple secondaries the calculations above have to apply to each connection combination.
How do you determine Push-Pull Output transformer Primary connections.
Most of our push pull transformers are wound in several sections.
These have been adjusted to provide tappings for Ultra Linear operation.
For a winding of 2000 turns anode to anode the winding would be:
- Centre tap to 20% UL tap = 200 turns (20% of ct-a)
- 20% UL to 43% UL = 230 turns (23% of ct-a) = 430 turns from centre to 43% UL.
- 43% UL to anode = 570 turns (balance of winding)
- The above are repeated for the other anode.
- These are sequenced to maximise transformer action between primary sections.
- These are interleaved between sections of the secondary to minimise leakage inductance.
Back to Menu: Product Technical
[2.5] Special and Custom Transformers and Chokes
Special versions
We offer a wind to specification service.
This service is popular and is usually operating at full capacity.
This service uses the same resources as Rewinding.
A typical waiting time will be as listed on the Rewinds page.
I want a transformer for a circuit that I can send you. Can I send the circuit?
To reduce overloading please do NOT send us large pictures of circuits etc unless agreed.
We will normally give you a special email address.
These large files may block our ISP server for several days.
Back to Menu: Product Technical
[2.6] Rewind and Replacement Transformers and Chokes
Rewind
We offer a rewind or replacement service.
This service is popular and is usually operating at full capacity.
A typical waiting time will be listed on the Rewinds page.
If a time is not listed then assume from 6 months to 2 years!
DO NOT send us transformers unless agreed.
Please add full name, address and contact details securely to transformer.
We have a number of transformers for rewind without any details.
If you have sent us a transformer and not received any progress reports recently then contact us.
Back to Menu: Product Technical
[2.7] Part Numbers, Sales Codes and Drawing Numbers
The numbers on the delivery notes or labels are confusing.
Normally we would provide Salescode, Drawing number and Internal order.
Our sales codes are in the format VXX123456.
These refer the designs which are given drawing numbers in the format DXX12345-0000.
A cross reference between a drawing number and salescode is given near the bottom of each data sheet.
Special and Rewind transformers are allocated a drawing number only.
Internal Orders are four our use only are are in the format AXX12345.
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[2.8] Products undergoing Design Changes.
What products are likely to change in the near future?
We have finished changing products as a result of material supply and machine process problems.
We may have minor corrections to connections and data.
What if I want a Transformer to Match or Replace an earlier design?
We keep the design of all earlier issues on File and can make to special order.
There may be a charge for this service.
Back to Menu: Product Technical
[2.9] Safety
How safe are your Transformers
See also LVD Directive below.
We use high quality professional materials.
Mains transformers use separate sections for Primary and Secondaries.
Insulation between windings is a composite of Nomex and Polyester tapes.
All except certain rewinds (where we meet the original specifications), or very small transformers (where we use an appropriate voltage) are
tested at the equivalent of 4000 VRMS.
All materials are UL approved. We also do our own flammability tests on combinations of varnish and winding materials.
Any faults are rigorously investigated within our FRACAS system.
All our products are made within our ISO9001 - Quality Management System.
We meet all the technical requirements to enable us to CE mark our products.
Back to Menu: Product Technical
[3.1] Low Voltage Directive
Do you meet the LVD (Low Voltage Directive)?
We meet the requirements of Directive 73/23/EC
Specification EN60950 is used as a detailed interpretation.
Yes - in all respects.
Are your transformers safe?
We comply with all the relevant sections of EN61558.
Mains transformers are double insulated.
No metal screen is fitted.
All VALVE transformers are tested for safety isolation.
Voltage proof from winding to frame is tested at 4000 Volts RMS or equivalent.
Voltage proof from winding to winding is tested at 4000 Volts RMS or equivalent.
Older type transformers such as rewinds meet the requirements in force at the time of original design.
We have no control over installation and use of our transformers.
We assume that anyone capable of choosing one of our transformers is competant to use it.
Back to Menu: EU Directives
[3.2] EMC Directive
Do you meet the EMC (ElectroMagnetic Compatability Directive)?
Directive EEC 89/336/EC
This does not apply directly to conventional transformers.
For Power Supplies and Inverters we create a technical file with a combination of Design notes, Simulations and Test results.
We use MIL-STD-461F, Def-Stan 49-411, RTCA DO160-D and MIL-STD704E as guidelines.
Back to Menu: EU Directives
[3.3] RoHS
Do you meet the RoHS (Restriction of Hazardous Substances)?
We comply with Directive EEC 2002/95/EC
Rewinds and replacement transformers for products made before July 2006 are exempt.
New products (including valve amplifiers to earlier designs are compliant).
We are colour coding all product shipped from June 2006.
Green dot or no marker indicates full compliance.
Red dot indicates non compliance (eg old stock or exempt).
Yellow dot indicates partial compliance or mixed materials.
Blue dot indicates full compliance with extra Tin Whisker mitigation processes.
Yellow dot product is usually only made for internal or prototype items.
Back to Menu: EU Directives
[3.4] WEEE Directive
Do you meet the WEEE (Waste Electrical and Electronic Equipment)?
Directive EEC 2002/96/EC
Most of our product is classed as a component used within a larger item.
As such it will be recycled by the end manufacturer.
However any product returned to us will be dismantled and recycled.
Where possible reject and returned transformers are dismantled.
All useable parts are returned to stores (may be quarantined for internal use only).
Scrap copper and iron is sold to our local scrap dealer.
Back to Menu: EU Directives
[3.5] ISO 9000 / 9001
Are you approved to ISO9000?
Yes to ISO9001:2001 by QMS International PLC - at the first attempt.
We have been audited succesfully to the later vaersion - ISO9001:2008.
Back to Menu: EU Directives
[3.6] Military and Professional
Can you work to Military and Professional Specifications?
We have supplied product and design services to most of the Avionics and similar companies.
Call us for more details.
Some relevants specifications are:
- Designed to meet MIL-T-27.
- Regulation to meet MIL-STD-704E.
- EMC (where relevant) to meet MIL-STD-461F.
- EMC (where relevant) to meet Def-Stan 59-411.
- General requirements to RTCA DO160-D.
- General requirements to EN60950.
- Safety to meet EN61558.
- Reliability to keep stress ratings low for MIL-HDBK-217F N2.
- Design services to ESA requirements.
We have been assessed to ISO9001:2008 sucessfully.
Back to Menu: EU Directives
[3.7] REACH Directive
Do you meet the REACH regulations?
Most chemicals that we use are in relatively small amounts.
These do not require declaring to REACH authorities.
Back to Menu: EU Directives
[4.1] General Website Notes
Some of your products seem to have been removed from the website. Why?
We recently restructured our website.
It was not possible to upgrade all our datasheets at once.
We can still supply all previous products.
Back to Menu: Website Technical Notes
[4.2] Cookies
Do you use cookies?
We no longer use Cookies.
Note that you will still require to enable 'Java' on our Price Calculator Page.
Back to Menu: Website Technical Notes
[4.3] Viruses and Spyware
Do you Virus Check E-Mails?
We use Norton AntiVirus to check all E-Mails in and out.
This is updated each time we go online.
We also have Spybot S & D and Malwarebytes.
All our data is scanned prior to upload onto our server.
Back to Menu: Website Technical Notes
[4.4] SPAM
How do you deal with SPAM?
Our Server marks most of the SPAM emails for use.
These are deleted un-opened.
Other Emails that appear to be SPAM are also deleted un-opened.
Any supplier who sends us several Emails (particularly large ones) is deleted from our approved suppliers list.
Any Email without a valid 'To' address is deleted.
Any Email with a dodgy title is deleted.
We never send SPAM out.
All our emails are sent to one address.
We also 'cc' these for internal use and to confirm successful transmission.
Back to Menu: Website Technical Notes
[4.5] JavaScript
I can't access your JavaScript calculator pages.
You may have JavaScript processor disabled.
Try one of the following:
- Enable JavaScript processor.
- For UK use use the UK prices page.
- For export Email us - but check your location on this page.
Back to Menu: Website Technical Notes
[4.6] Website Design
How is the Site created?
All top level pages are coded in HTML4 using Microsoft Notepad.
Data sheets are generally coded using home grown Visual Basic 5 Active-X modules which create HTML4 pages.
Calculating pages (eg Price Calculator) are coded using JavaScript and HTML4.
A standard Style sheet is used to control the appearence of all pages.
Images are compressed to reduce download time.
Back to Menu: Website Technical Notes
[4.7] Feedback and User Forum
Is there a feedback system or a means for contacting other customers?
There will be a User Forum in the future - as soon as we have spare software time.
This will be powered by Snitz Forums (see 'forum.snitz.com' for details on how it works).
Back to Menu: Website Technical Notes
[4.8] Phorm
Do you use Phorm to get or use information on visited sites?
We do not subscribe to Phorm - We disagree with it's principles of privacy invasion.
Back to Menu: Website Technical Notes
[5.1] Can't contact
Why can't I get a reply to Telephone, Emails or Voice Mail?
Leave a message on voicemail or email the sales office.
It may be several days before we can deal with your enquiry.
Telephone sales line is normally available between 11am and 4:30pm Mondays to Thursdays.
Voicemail, email or Fax during staff holidays.
Voicemail messages are often difficult to understand due to background noise etc.
Voicemail users should leave a telephone number that they can be contacted on, and the times that they will be available.
Back to Menu: Communications
[5.2] Emails
How do we handle Emails?
We have several Email accounts.
The main ones are shown on our Index page.
This allows us to monitor the source of the enquiry.
We also have a Email account for design department follow up correspondance.
Pick the most appropriate address to send to. We will route to the correct person.
It is not necessary to send to all addresses. If you do you may get several conflicting replies.
Back to Menu: Communications
[6.1] Supplier ?
How do we become a supplier to VVT Ltd?
Do not send us sales literature or SPAM.
If you feel that you have a service or supply that would be useful to us, send us a SMALL
text email with your website address.
We automatically delete anyone who SPAMs us from our potential suppliers list.
Back to Menu: Company
[6.2] Where?
Where do you make your transformers?
All our transformers are designed, manufactured and tested on the Isle of Wight.
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[6.3] Isle of Wight
Is the Isle of Wight part of the UK?
The Isle of wight is a county in England UK.
It is about 2 miles off the coast of southern England.
Standard UK trading rules apply.
Company is Registered in England.
Back to Menu: Company
[6.4] Contact and address
Where do I get contacts and accounts office information?
From our Index page (home page)
Link to Home Page and Contact Details
Back to Menu: Company
[6.4] Variable Voltage Technology
Why are you called Variable Voltage Technology Ltd?
When we first started trading (in 1987) we specialised in Electronic Bench Variable Power Supplies.
At that time we bought in our transformers.
Eventually we changed suppliers and finally took over our transformer supplier.
We have concentrated since then on supplying transformers into a wide range of markets.
We have never made Variable Voltage Transformers (eg Variacs) despite our name.
We do design and make specialist Electronic Power Supplies (including Variable Voltage) to order.
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[7.1] Warranty
Do you guarantee your transformers?
All our products are guaranteed for normal operation for one year.
As these are generally fitted by the customer we can take no responsibility
for any injury or consequential damage occured.
If you have any problems with our products let us know as soon as possible so that we can resolve the issue.
We will replace, redesign or refund as agreed.
We operate a 'FRACAS' database for 'Fault Recording And Corrective Action System' at all levels of our business.
You will be allocated a FRACAS code (eg X12345) for a particular problem.
Back to Menu: Terms and Conditions
[7.2] Damaged in transit
Damaged in Transit?
Call us IMMEDIATELY.
We will discuss repair and or replacement under warranty.
Please keep any packing and Carrier information.
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[7.3] Trading Rules
Simplified Terms and conditions of trading.
We reserve the right to cancel an order due to payment problems or supply problems.
All orders must be paid for at the time of ordering unless a trading account has been set up.
Credit cards will be transacted when product has been tested.
Cheques will be presented when product has been tested.
Rewinds will be invoiced as soon as feasability has been confirmed.
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[7.4] Invoices
Invoices.
Invoices are generated where appropriate or on request.
VAT is identified where appropriate and is charged at the current UK rate at the time of delivery.
Most standard product has VAT included at the current rate.
Invoices must be paid with 30 days of the invoice for single orders.
For monthly accounts Balances must be paid within 7 days of statements.
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[7.5] Overdue Accounts
Overdue Accounts
Charges may be payable on overdue outstanding accounts.
These charges are based on the concept that you are borrowing money from us instead of a Bank.
Therefore we charge as if we were a bank.
Charges are our discretion and may include any or all of the following:
- Interest at NatWest Mastercard rate from day to day.
- Daily overlimit charge of £3.50 per day.
- Charges monthly compounded.
- Chase letters charged at £27.50 each added to account.
- If the amount including charges exceeds £1500 we will issue a Winding Up Order.
- All these are subject to change without warning.
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[7.6] Design Changes Policy
Design changes and Alternative Parts.
We reserve the right to change to design of any product without warning.
This may be due to Material availability, Plant breakdown, Process problems or any other cause.
Where possible we will notify you.
If the changes are unacceptable to you, you may cancel the order without charge.
We will not accept any costs as a result of such changes.
[7.7] Design Changes Policy
Inability to supply.
We reserve the right to remove product or cancel orders if we are unable to supply a previously agreed order.
This may be due to Material availability, Plant breakdown, Process problems or any other cause.
This may happen at any time from enquiry to Delivery.
Back to Menu: Terms and Conditions
© 2009 Variable Voltage Technology Ltd. Data Sheet Number DCW13271.