How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Pete Your Own Question
Pete, Engineer
Category: Electronics
Satisfied Customers: 19730
Experience:  Over 16 years of experience in the Electronics and IT industries.
Type Your Electronics Question Here...
Pete is online now

I own a Panasonic Digital Cordless Telephone system

This answer was rated:

Good morning. I own a Panasonic Digital Cordless Telephone system KX-TCD420E which is now 12 years old.
My BT landline gives me access to the Panasonic Base station (and three other wireless connected handsets), a further conventional telephone handset (not wireless connected to the Panasonic system), and my BT Infinity system which drives both the desk-top computer and the Smart TV. All systems were in A1 condition until recently.
Suddenly, and for no apparent reason known to me, the telephone system started generating firstly 'mains hum' and then heavy cracking noises too. The phones are all now unusable whilst the BT Infinity system remains perfectly fine.
Each of the 4 Panasonic handsets are indicating the following displays: (a) flashing 4 dot battery icons dots), which I understand indicates 'fully charged' and (b) the number '25'.
One the handsets is actually showing '[4] 25'. Are these error codes etc ?
I have read the Operating Instruction manual, changed both ASDL filters to the Panasonic and free-standing phone, but still have this terrible line 'interference' which I cannot solve . The manual does not seem to cover the above fault-finding scenario!
Is this something which I need to pass onto BT and/or what other advice could you offer please?
Many thanks.
John Abbess

Hi John,

The BT Infinity system uses fibre optic cable, whilst the phone system uses plain old copper wire, so that helps explain why it is working perfectly.

The crackling may be caused by bad wiring, or it could be due to a fault with the Panasonic phone system.

Do you have any other devices connected to your landline at all? (e.g. alarm system, fax machine)

Does the conventional telephone work ok, or do you hear crackling on it as well?

Does the conventional telephone work ok if you unplug the Panasonic system from the telephone line and connect the conventional telephone to master BT socket in your home?

Your satisfaction is my priority;
Kindly take a moment to rate my service 5 stars at the top of your question page so I am rewarded for my time; tips appreciated :)
You can always reply back at any time if you need any further assistance at all.

Customer: replied 1 year ago.
Hi Pete,
Very pleased that you are responding so quickly. I am indeed grateful. TKU.
Before I answer your very clear and specific questions, here are just a few additional thoughts which might be important please....
The system configuration here is somewhat complex to explain, as will become more apparent in my response to you.
Meanwhile, as a general rule, everything here has been 'generally quiescent' for several weeks to the best of my knowledge (ie) this problem has simply just appeared and worsened for reasons unclear to me . However, I did have a fault on the desktop computer which required external professional help and some temporary moving of equipment ,some 4 weeks previous to this latest problem......perhaps some wiring and /or equipment location was/were marginally disturbed, and the impact has only just surfaced?. I will have to have another poke around later!..
Next point is that 2 months or so before that, I needed Open Reach to attend to my then-dire BT Infinity service and the engineer fitted some new (non-standard?) filtering system at the master BT socket location, and for several weeks after his work, everything on my system was just fine.
Onto your specific questions...... I do indeed have a house alarm connected ,but this no longer communicates down the landline to the control centre (this being the case for at least 4 years). The security alarm control unit is set up to audibly alarm when the unit is opened (it thinks it's an unauthorised attack!), so accordingly I do not attempt to do so ALTHOUGH there IS the looped extension from this box onto the conventional telephone. Below the alarm box sits a mains single-ganged switch which may or may not have been switched off accidentally by me and which may or may not be relevant to this scenario.
Onwards ....................Both the conventional phone AND the Panasonic system experience crackling.
Even when I unplug the Panasonic system I hear crackling on the conventional phone and vice versa....... furthermore, even when I swop their physical locations within the house (ie) connect the Panasonic system alone into the 'normal' socket location for the conventional phone, and vice versa.
I cannot now access the BT master socket because this is where Open Reach have now installed this special filtering arrangement which is completely different from their normal socket arrangement (it is metaphorically, a sealed black box).Before your respond again, two last thoughts enter my mind (a ) is Code 25 significant on the handset displays? and
(b) would it be wise to pay someone to attend here, with perhaps some replacement Panasonic phones..... and at what cost?RegardsJohn
Customer: replied 1 year ago.
I am not quite sure what 'securely connect' actually equals, but I suspect that there is a problem with the quality of the incoming BT line, given all of the information that I have presented.
Please verify/confirm etc.
Thank you.

Thanks for the detailed response, John.

You can ignore the automated offer of remote assistance, it is sent by the site automatically and is not relevant to your question.

I've been looking further into the phone system to find out what the '25' might mean - it is not an error code, so it indicates something else, perhaps the number of missed calls or the number of voicemails waiting to be listened to.

If you could attach a photo of the display I might hazard a better idea as to what it means.

As the conventional phone is also affected, this is likely a line issue. First, check all internal wiring to make sure none is damaged or badly connected if anything was moved recently, or if pets might have gnawed the line, etc.

If all checks out ok then it will be up to BT to find where the line fault lies - it could be that floodwater has gotten into an underground cable somewhere, or a tree branch is touching an overhead wire, or something similar is causing the crackling on the line.

Customer: replied 1 year ago.
Hi Pete,Perfect ... TKU.I will give BT a call on my mobile when I get the chance tomorrow and amongst other things, refer to these exchanges today.Meanwhile, many thanks for your assistance, which has helped me move matters forward.John

John, you are very welcome!

Enjoy the rest of your weekend.

Kindly take a moment to leave a rating for my service on your question page.

Many thanks,


Pete and other Electronics Specialists are ready to help you