How is it possible to hear the dial-tone, etc., with the handset unplugged?

[MaximRecoil]

I unplugged the handset from my WE 2500 to test a different phone that doesn't have a handset, which of course took it off the hook. About a minute later I was surprised to hear the off-hook warning coming from the 2500's base. So I pressed the hook switch down and released it, and put my ear right to the phone, and found that I could faintly hear everything, i.e., the dial-tone, then the recording of the lady who says, "If you'd like to make a call, please hang up and try again...", and then the off-hook warning, which is loud enough to hear even without my ear pressed to the base of the phone. You need a speaker to hear those things (or "receiver" in telephony terminology), so where is the speaker in a 2500?

I also tried it with a WE 500 and there was nothing, just dead silence like you'd expect.

Edit: I just tried it with a different 2500 (don't know the brand; definitely not WE though) and the results were the same as with the WE 500, i.e., dead silence.

[Key2871]

 Well that's a new one for me.

[FABphones]

I unplugged the handset from my WE 2500 to test a different phone that doesn't have a handset, which of course took it off the hook. About a minute later I was surprised to hear the off-hook warning coming from the 2500's base. So I pressed the hook switch down and released it, and put my ear right to the phone, and found that I could faintly hear everything, i.e., the dial-tone, then the recording of the lady who says, "If you'd like to make a call, please hang up and try again...", and then the off-hook warning, which is loud enough to hear even without my ear pressed to the base of the phone. You need a speaker to hear those things (or "receiver" in telephony terminology).....

It must have formerly been the carphone in 'Christine'....

[MaximRecoil]

Here are some pictures of the phone. That little white plastic thing is just an insulator that snaps over the spade terminals of some unused wires, and that larger plastic rectangular pink box houses a polarity guard (part #840364202). The network is a 4228.

[Key2871]

That white thing joins Spade ends to make a connection point.

[MaximRecoil]

That white thing joins Spade ends to make a connection point.

Okay, but that doesn't seem to be a good method of making a solid electrical connection. Either way, as a test, I removed the white plastic thing and kept the 3 spade terminals that were in it separated, and the phone still functions 100%, and it still does the thing where you can hear the dial-tone, etc., with the handset unplugged.

[AL_as_needed]

Not sure how dial tone would be possible without a handset. Could there be an  issue with the tone generators in the key pad picking up stray voltage?

[andre_janew]

Stray voltage could be coming from terminals touching other nearby

terminals by way of the spade connectors.  Also check wires for bare spots.

[MaximRecoil]

Stray voltage could be coming from terminals touching other nearby

terminals by way of the spade connectors.  Also check wires for bare spots.

How does stray voltage reproduce the sound of a human voice without a speaker?

[Owain]

Speech currents may be flowing through the bell coils, especially if the handset is out of circuit, and the coils or bell motor may be vibrating slightly, just as you can hear a mains frequency hum from a transformer.

[Key2871]

Company's used those a lot when terminals were not available. You'd be surprised it actually works pretty well.
I don't think it's why you here side tone when the handset is in plugged.

[HowardPgh]

There is probably a loose lamination in the coil in the network. When there there is no load from the receiver, the energy normally used to operate the receiver is enough to vibrate the loose lamination.

[Partyline4]

Something is picking up the AC signal, likely the bell coil, and the noise is being mechanically expressed.... like an old crystal radio, sometimes the signal can be so strong the crystal vibrates and noise is heard.

Probably a 1/1000000 thing to happen....

Neat nontheless

[19and41]

I've never had a WE induction coil apart.  Did they use a laminated iron core or a dual ferrite "E" core"  I used to perform QA testing on power supplies and if the "E" cores wern't fully mated properly they would resonate with whatever audio frequency signal was put on the coil or transformer.

[MaximRecoil]

I got another WE 2500 in the mail yesterday, and I can hear the dial-tone, etc., with the handset unplugged on this one too. Like the other one, it has a 4228 network, but instead of a type 35 keypad it has a type 72 keypad.

My other 2500 that I mentioned in my edit of my first post, unknown manufacturer, has an ITT 427 type network. As I said in my first post, I thought that one didn't do it, but I tested it again just now, and it actually does do it. However, it is much quieter than the already quiet Western Electric ones. It is so quiet that I can't hear the dial-tone or the recording of the "If you'd like to make a call..." lady, even with the shell removed and my ear right up close, but I can hear the off-hook warning. With the two Western Electric ones, the dial-tone and recorded lady's voice can only be heard with your ear pressed to the phone, but the off-hook warning is loud enough to be heard from across the room.

Furthermore, I retested a WE 500, and the off-hook warning can be heard with it too, albeit at the same very low volume as with the off-brand 2500 (which is why I didn't notice it the first time I tested it).

I'd say that rules out it being a phone issue, so either there's something special about my ostensibly ordinary POTS line, or other people just haven't listened close enough to their 500s or 2500s (and probably many other models of phones) to hear it before. I suggest trying it out if you have a POTS line (I don't know if it would do it on a VoIP line or not). Put your ear right up to that big hole in the bottom of the phone that's under the dial/keypad:



Edit: I tried it with the only modern phone I have, a Sony IT-B3 from 1995, and the results were the same as with the 500 and the off-brand 2500, i.e., too quiet to hear the dial-tone or the recorded lady, but I could faintly hear the off-hook warning. That rules out it being the bell coil, because this phone doesn't have a bell ringer.