ADSL customers can look forward to a free broadband speed boost, after BT Wholesale started delivering a new piece of hardware to ISPs that filters out electrical interference in the home to provide more stable connections and faster downloads.

The product, called I-Plate, was announced by BT earlier this year, but the telecom giant only started distributing it to its partner ISPs today.

It's designed to block interference from televisions, lighting and home wiring, which BT says can slow down home broadband speeds.

The company said the seven out of ten UK homes with a BT NTE 5 master socket are eligible for an I-Plate, and claimed that in its study of 36,000 lines, the technology typically showed a speed increase of up to 1.5Mbps. Some lines showed speed improvements of as much as 4Mbps.

As well as boosting overall speeds, BT said the technology could prove a bonus for ADSL customers who live some distance from their local telephone exchange, while the minority of people who were previously just beyond the reach of a broadband service, may now be able access the high-speed web.

"The BT NTE 5 master socket can be easily identified by the horizontal split in the face plate and BT logo," said BT. "All consumers need do is simply unscrew the face plate, clip the I-Plate in place in the socket and replace the face plate over the I-Plate."

But customers must contact their ISP, rather than BT Wholesale, to get their hands on an I-Plate. BT has previously estimated that the device would cost end users around £10, but more recently suggested that some ISPs may offer it to customers for free. But the telecom giant warned that not all ISPs would offer the I-Plate immediately.