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

[dsk]

The nature of a receiver is a coil making a variable magnetic field this has to use its magnetic force to move something with iron, to not double the frequency we need a polarization made by a magnet or DC current. what may fulfill these demands?

As mentioned over, the ringer, it is a suitable coil, a magnet and something to move, Since the ringer usually not are made to be resonant at frequencies over 60 Hz, the sound will barely be hearable, but if it is a quite environment, and you here well it may be possible. What else, anything else containing a coil, e.g. the induction coil. It may be polarized by the DC path, and a bad core may vibrate, that's why we sometimes hear the humming from transformers connected to the mains.

The only way to be sure is to try again, and eliminate by touching the parts, and see (hear) when it stops.


dsk

[CanadianGuy]

Any chance you could take a video and share it? I always love seeing anything odd with POTS lines, since that's what I do for a living. The phone network still does some weird things sometimes, but probably nothing like the old days of step-by-step or panel offices. I wish I could've seen that in action. All the offices I've been in were converted to Nortel DMS around the late 70s or early 80s I'm assuming.

[MaximRecoil]

Any chance you could take a video and share it? I always love seeing anything odd with POTS lines, since that's what I do for a living. The phone network still does some weird things sometimes, but probably nothing like the old days of step-by-step or panel offices. I wish I could've seen that in action. All the offices I've been in were converted to Nortel DMS around the late 70s or early 80s I'm assuming.

https://youtu.be/5bcFqrDs21o

[Pourme]

That is wild!

Thanks for posting!

[FABphones]

I heard it until it was unplugged, then silence. 

Then I remembered, I have my volume down low..... 

Thanks for the clip.

[Partyline4]

What about the noise when you hold down the hookswitch? 

Ac hum of some sort....Some phones seem to get it worse than others....North telecom one's for me especially...

[MaximRecoil]

What about the noise when you hold down the hookswitch? 

All of my phones are 100% silent when the hook switch is held down. I have a WE 500 that made very faint staticky noise that you could hear if you held the receiver to your ear while holding down the hook switch, but cleaning the hook's leaf switch contacts fixed that.

[rdelius]

on a 500 set ,you will not hear anything in the receiver when the hookswitch is depressed because there are shunt contacts to protect your ears from noise

[MaximRecoil]

on a 500 set ,you will not hear anything in the receiver when the hookswitch is depressed because there are shunt contacts to protect your ears from noise

The shunt contacts don't completely mute the receiver, neither the ones linked to the hook switch nor the ones linked to the dial. But I was talking about noise while the hook switch is already all the way down, rather than while it's being depressed. All phones' receivers should be completely silent while they are on the hook.

[Partyline4]

Well, I'm here to tell you that some of my phones DO make a noise when hook switch is depressed 

[MaximRecoil]

Well, I'm here to tell you that some of my phones DO make a noise when hook switch is depressed 

What kind of a noise? If it's a staticky noise, then cleaning the hook's leaf switch contacts will normally fix it.

[Partyline4]

What kind of a noise? If it's a staticky noise, then cleaning the hook's leaf switch contacts will normally fix it.

Its like a square wave sound if you can understand that, definitely a non sinusoidal waveform. Faint, but audible ...

[19and41]

Whichever component(s) make the noise. it is most likely a mechanical resonation and will take on the characteristic of that which makes it.  I'd say any items containing a coil and core is a suspect.

[TelePlay]

https://youtu.be/5bcFqrDs21o

     Regular Member Post

Recording the YouTube audio with Audacity, removing the noise from the faint (handset disconnected) portion and then normalizing that faint portion (amplifying the wave form), it shows

1) the original is a square wave form sent at 5 "pulses" per second with the space between tones equal to that of the tone.

2) due to the near inaudible recording of the disconnected signal, the tone form seems to be a square wave as well but the clarity of the wave is not seen due to noise removal and amplification of the signal left after noise removal.

3) the slight offset may be due to cutting and pasting the waveform into a new track to make the comparison


The "disconnected" tone is there, it is faint and it is similar.

If the recording device could be placed closer to the source of the sound within the phone once the handset is disconnected improving the signal to noise ratio of the faint sound, the wave form of the faint sound would or should have better resolution that that of the attached image. The best recording position would be at a point where the sound from the handset and from the sound from the housing after the handset was removed would be about equal in amplitude.

The handset can always be pushed further away from the phone to reduce its level to make it about equal to the sound from the phone with the handset disconnected.

One suggestion would be to use a small, sensitive microphone and move it around the phone (with the housing removed) to see where the "disconnected" sound is the loudest, its source, what component is producing the sound.

[MaximRecoil]

Interesting post. Unfortunately, I don't have a microphone other than the one I used. And I can't detect the source of the sound by ear or by touching the coils to feel for vibration, because the sound is too faint. I need a mechanic's stethoscope.

So no one else's phones do this on their line? Like I said before, all my phones do it to one degree or another (in terms of volume), including a relatively modern Sony IT-B3, so it's not caused by my phones. If no one else's phones do this on their line, then there must be something unusual about my phone line, even though it's a normal POTS line that has been in place for ages. The only thing unusual about it that I've noticed is the ancient, very thick wiring that is the primary feed for all the jacks. It is 20 AWG (I measured it with calipers; it's 0.032" diameter), which is massive for telephone wire, considering most telephone wire these days is 24 to 26 AWG:



The wiring coming out of the jack on the right is some new stuff that I ran to my payphone, and it's thicker than normal (it's 22 AWG), but it's dwarfed by that old 20 AWG stuff on the left.