Years ago with POTS if you got a constantly engaged tone you could phone
the operator and ask if there really was someone on the line. They could check and tell if there was a conversation going on or not, and perhaps
the phone had been left "off the hook".
I assume that this is still possible with purely analogue lines in some
way, but what about Digital Voice?
Years ago with POTS if you got a constantly engaged tone you could phone
the operator and ask if there really was someone on the line. They could >check and tell if there was a conversation going on or not, and perhaps
the phone had been left "off the hook".
I assume that this is still possible with purely analogue lines in some
way, but what about Digital Voice?
Years ago with POTS if you got a constantly engaged tone you could
phone the operator and ask if there really was someone on the
line. They could check and tell if there was a conversation going on
or not, and perhaps the phone had been left "off the hook".
I assume that this is still possible with purely analogue lines in
some way, but what about Digital Voice?
Can operators listen in on digitally switched analogue calls? I thought
that is something that needs a wire tapping permission (police warrant
etc)?
Jeff Layman <Jeff@invalid.invalid> wrote:
Years ago with POTS if you got a constantly engaged tone you
could phone the operator and ask if there really was someone on
the line. They could check and tell if there was a conversation
going on or not, and perhaps the phone had been left "off the
hook".
I assume that this is still possible with purely analogue lines
in some way, but what about Digital Voice?
Can operators listen in on digitally switched analogue calls? I
thought that is something that needs a wire tapping permission
(police warrant etc)?
Jeff Layman <Jeff@invalid.invalid> writes:
Years ago with POTS if you got a constantly engaged tone you could
phone the operator and ask if there really was someone on the
line. They could check and tell if there was a conversation going on
or not, and perhaps the phone had been left "off the hook".
I assume that this is still possible with purely analogue lines in
some way, but what about Digital Voice?
I get an engaged tone when people hang up at the end of the call. I
think it comes from the router. It's probably the VOIP equivalent of
"Oops, something went wrong".
On 14/04/2026 13:22, Richmond wrote:
Jeff Layman <Jeff@invalid.invalid> writes:
Years ago with POTS if you got a constantly engaged tone you couldI get an engaged tone when people hang up at the end of the call. I
phone the operator and ask if there really was someone on the
line. They could check and tell if there was a conversation going on
or not, and perhaps the phone had been left "off the hook".
I assume that this is still possible with purely analogue lines in
some way, but what about Digital Voice?
think it comes from the router. It's probably the VOIP equivalent of
"Oops, something went wrong".
It seems strange that an engaged tone should be used when the
connection has been terminated; if you hang on long enough does it
change to a "call terminated" tone? What tone do you get when you dial
an unobtainable number?
Jeff Layman <Jeff@invalid.invalid> writes:
On 14/04/2026 13:22, Richmond wrote:
Jeff Layman <Jeff@invalid.invalid> writes:
Years ago with POTS if you got a constantly engaged tone you couldI get an engaged tone when people hang up at the end of the call. I
phone the operator and ask if there really was someone on the
line. They could check and tell if there was a conversation going on
or not, and perhaps the phone had been left "off the hook".
I assume that this is still possible with purely analogue lines in
some way, but what about Digital Voice?
think it comes from the router. It's probably the VOIP equivalent of
"Oops, something went wrong".
It seems strange that an engaged tone should be used when the
connection has been terminated; if you hang on long enough does it
change to a "call terminated" tone? What tone do you get when you dial
an unobtainable number?
I don't know, but I suppose if I got an engaged tone, I wouldn't know if
it was unobtainable or engaged.
What's an example of an unobtainable number?
On 18/04/2026 22:32, Richmond wrote:
Jeff Layman <Jeff@invalid.invalid> writes:
On 14/04/2026 13:22, Richmond wrote:I don't know, but I suppose if I got an engaged tone, I wouldn't
Jeff Layman <Jeff@invalid.invalid> writes:
Years ago with POTS if you got a constantly engaged tone you couldI get an engaged tone when people hang up at the end of the call. I
phone the operator and ask if there really was someone on the
line. They could check and tell if there was a conversation going on >>>>> or not, and perhaps the phone had been left "off the hook".
I assume that this is still possible with purely analogue lines in
some way, but what about Digital Voice?
think it comes from the router. It's probably the VOIP equivalent of
"Oops, something went wrong".
It seems strange that an engaged tone should be used when the
connection has been terminated; if you hang on long enough does it
change to a "call terminated" tone? What tone do you get when you dial
an unobtainable number?
know if
it was unobtainable or engaged.
So if you were given a phone number (making following a car accident
and exchanging details with whoever gave you that number), and you
phoned it and it was constantly engaged, you couldn't tell if it was genuinely engaged or, for example, an unobtainable fake number.
I guess a few years ago you could call the BT operator to check, but
how do you do it now? There are websites which claim to be able to
check whether or not any number is real.
What's an example of an unobtainable number?
Not sure for certain how to find one. I tried the Experian
confirmation utility at <https://www.edq.com/phone-verification/> by
testing it with +44 800000000 and it reported:
"No coverage
Unable to detect the live status for the telephone network."
So I called 0800000000 and found it was a number for The Prudential!
I decided to change tack and search on "UK telephone reserved
codes". At <https://en.wikipedia.org/wiki/List_of_dialling_codes_in_the_United_Kingdom#Code_prefixes>,
it states that phone numbers beginning 04 and 06 are reserved codes,
but doesn't explain what that means. Just for confusion, at <https://en.wikipedia.org/wiki/Telephone_numbers_in_the_United_Kingdom#Structure>
it says that 04 and 06 are "Not in use"!
I tried 04123456789 from my mobile and got the engaged tone. I then
tried 06123456789 and got the same thing. I don't use my mobile for
many calls, and haven't to my knowledge called an unobtainable number
before, although I've had an engaged tone calling numbers I know are
ok. Looks like Voip calls and mobile calls treat unobtainable numbers
in the same way. I wonder why; is it because they're digital? What
about DV (non-Voip) calls?
I decided to change tack and search on "UK telephone reserved codes". At <https://en.wikipedia.org/wiki/ List_of_dialling_codes_in_the_United_Kingdom#Code_prefixes>, it states
that phone numbers beginning 04 and 06 are reserved codes, but doesn't explain what that means. Just for confusion, at <https:// en.wikipedia.org/wiki/Telephone_numbers_in_the_United_Kingdom#Structure>
it says that 04 and 06 are "Not in use"!
___ _ ___ _
__ __ __ __ __This is "subscriber engaged", where the phone is ringing or off hook.
On 19/04/2026 14:11, Richmond wrote:
___ _ ___ _This is "equipment engaged", and is the tone equivalent of "all lines
to xxxx are busy, please try again later". Done correctly, one length
is louder than the other.
__ __ __ __ __This is "subscriber engaged", where the phone is ringing or off hook.
"Number unobtainable", which is what you are looking for, is a
continuous tone, although normally replaced by a voice announcement.
David Woolley <david@ex.djwhome.demon.invalid> writes:
On 19/04/2026 14:11, Richmond wrote:
___ _ ___ _This is "equipment engaged", and is the tone equivalent of "all lines
to xxxx are busy, please try again later". Done correctly, one length
is louder than the other.
__ __ __ __ __This is "subscriber engaged", where the phone is ringing or off hook.
"Number unobtainable", which is what you are looking for, is a
continuous tone, although normally replaced by a voice announcement.
On my router there are two phone sockets and these have internal phone numbers **11 and **12 , so if I phone **11 from phone 1 I get a tone
which is actually the equipment engaged tone above, but it must be
coming from my router I guess because such a call need not go outside
the router. Or maybe these tones are actually transmitted as error code
and are then always translated into tones by the VOIP receiver or
router?
On 19/04/2026 21:56, Richmond wrote:
David Woolley <david@ex.djwhome.demon.invalid> writes:
On 19/04/2026 14:11, Richmond wrote:
___ _ ___ _This is "equipment engaged", and is the tone equivalent of "all lines
to xxxx are busy, please try again later". Done correctly, one length
is louder than the other.
__ __ __ __ __This is "subscriber engaged", where the phone is ringing or off hook.
"Number unobtainable", which is what you are looking for, is a
continuous tone, although normally replaced by a voice announcement.
Aren't these SS7 call status tones
On my router there are two phone sockets and these have internal phonewell of course the call status is transmitted as a status code. The
numbers **11 and **12 , so if I phone **11 from phone 1 I get a tone
which is actually the equipment engaged tone above, but it must be
coming from my router I guess because such a call need not go outside
the router. Or maybe these tones are actually transmitted as error code
and are then always translated into tones by the VOIP receiver or
router?
tones are generated locally! If the call isn't set up so you haven't
selected a codec so you can't send a tone. Not sure if this is the
current protocol defs...
https://datatracker.ietf.org/doc/html/rfc3261
David Wade <g4ugm@dave.invalid> writes:
well of course the call status is transmitted as a status code. The
tones are generated locally! If the call isn't set up so you haven't selected a codec so you can't send a tone. Not sure if this is the
current protocol defs...
https://datatracker.ietf.org/doc/html/rfc3261
You say 'of course' as if it is obvious, but it isn't obvious to
me. When I had an analogue line the tone would have been sent as a sound
over the line in the same way as a voice. So how do I know that if I
make a call to an analogue line the tone isn't created in the system somewhere and then sent as a sound (though digital) in the same way as
voice?
Or maybe these tones are actually transmitted as error code
and are then always translated into tones by the VOIP receiver or
router?
Aren't these SS7 call status tones
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