VDSL filters and ADSL filters - does it matter?

Modified on Sat, 11 Jan, 2020 at 4:25 PM

When upgrading an existing socket to VDSL (FTTC | GEA), it's possible that a previous ADSL faceplate will need to be removed and either replaced with a VDSL faceplate (recommended) or used with a suitable VDSL filter (not an ADSL filter). Here you'll find diagrams and links to the BT source documents.


There are a number of different face-plates that BT have supplied over the years, many do not display a version number. Here's a selection that do:



As you can see, the first one is only ADSL v1.0 compliant, the 2nd is ADSL 2+ and the 3rd is VDSL 2 compliant. The VDSL2 is backward-compatible.

If you are unsure of the type of face-plate, assume it's ADSL v1.0 - that means removing it if you plan to connect VDSL equipment.


Universal xDSL filter specifications are detailed in document ETSI Specification TS 101 952-1, available here: https://www.etsi.org/deliver/etsi_ts/101900_101999/10195201/01.01.01_60/ts_10195201v010101p.pdf

(Note sections A.2 and A.3 which detail the specific requirements for xDSL filters)


DSL versionFilter frequencies
[ Human voice | Fax ]300 Hz - 3.4 kHz
ADSL v.1.0 [ 8 Mbps ]138 kHz - 1.104 MHz
ADSL 2+ [24 Mbps ]138 kHz - 2.208 MHz
VDSL [ 40 Mbps ]138 kHz - 12 MHz
VDSL2 [80 Mbps+ ]138 kHz - 30 MHz


Here's a graphical diagram:


BT document SIN 498 outlines VDSL - you can download it here: https://www.btplc.com/SINet/SINs/pdf/498v7p5.pdf

(Pertinent section: "3.2.6 CPE VDSL2 Filter Requirements")


The equivalent ADSL document is BT SIN 346: https://www.btplc.com/SINet/SINs/pdf/346v2p11.pdf

Note sections "7.3 Additional notes about CPE filters" & "8. Out of band signals applied to the PSTN CPE", which explain the ADSL filter frequencies.



Best practice: fit the latest incarnation of VDSL2 filter for optimal xDSL performance, preferably a built-in face-plate.

Was this article helpful?

That’s Great!

Thank you for your feedback

Sorry! We couldn't be helpful

Thank you for your feedback

Let us know how can we improve this article!

Select at least one of the reasons
CAPTCHA verification is required.

Feedback sent

We appreciate your effort and will try to fix the article