On Thursday, May 21, 2015 at 7:43:36 PM UTC-4, Bill Horne wrote:

Here's a trip down memory lane: does anyone remember the IMTS
systems that preceded cellular? I find myself getting nostalgic
for the "good old days" of the mobile world, and I wonder if
any of that equipment has been converted to other uses.

Bill

Hi Bill,

I regularly get into conversations with 30 or 40-ish year olds that like to talk about the 'history' of mobile telephones. Their 'history' is the 3 watt bag phone that their dad had. They don't know there was 30 years of IMTS and before that MTS before the first AMPS trials in Chicago. I try to explain,
but they get blank looks on their faces.

I got my first IMTS phone in about 1975.....a 25 watt UHF Motorola "Green Weenie" trunk mount radio with a FACTS control head. Loved that thing. I had an employee at the time that just LOVED to switch to manual mode and listen to other conversations if he was waiting in my truck. He discovered that if we were parked close enough to a voting receiver location, he could manually key up and become the 'mobile' of the conversation. Shame on him.

I've been looking for a function generator app from which I can cut a ringtone or notification tone that has the alternating 1336 and 1800 Hz IMTS "disconnect" tones that the IMTS mobile would send out to the base when the mobile was 'hung up'. A second or two of it would play out over the circuit
to the landline caller before the terminal disconnected him. I always liked that signal, and would like to have it as a notification or ring tone for some special old friends from my IMTS days.

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Antenna Man <kenpda@gmail.com> wrote:

I've been looking for a function generator app from which I can cut a >ringtone or notification tone that has the alternating 1336 and 1800
Hz IMTS "disconnect" tones that the IMTS mobile would send out to the
base when the mobile was 'hung up'. A second or two of it would play
out over the circuit to the landline caller before the terminal
disconnected him. I always liked that signal, and would like to have
it as a notification or ring tone for some special old friends from
my IMTS days.

You should be able to manually generate 1336 and 1800 tones with
Audacity and edit them together.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On Tue, Nov 02, 2021 at 03:27:34PM -0000, Marc SCHAEFER wrote:

Antenna Man <kenpda@gmail.com> wrote:

I've been looking for a function generator app from which I can cut a >ringtone or notification tone that has the alternating 1336 and 1800
Hz IMTS "disconnect" tones that the IMTS mobile would send out to the
base when the mobile was 'hung up'. A second or two of it would play

Simple generation:

sox -V -r 48000 -n -b 16 -c 2 imts-disconnect.wav synth 30 sin 1336 sin 1800 vol -10dB

The file is on:

https://login.alphanet.ch/~schaefer/tmp/imts-disconnect.wav

You could then adapt the sox command line for your needs.

I remember that the IMTS phones that used VHF channels had push-
buttons that allowed users to access the older manual system:
they could press a push-to-talk button that was part of the handset,
and draw the attention of a mobile operator who would ask for their
mobile id, which consisten of a "Home" channel, followed by their call signalling code, followed by the city of registry (mine was JL-36446,
San Francisco).

When a manual system was cut over form "MTS" to IMTS, the units were
rewired so that they would respond to an ID made up of the area code
and last four digits of the associated POTS number: a design choice
that limited IMTS to fewer than 10,000 users per area code, per radio
band

UHF units, which were never used for "manual" service, had much
smaller control heads, which looked like overgrown Princess phones.

Bill

--
Bill Horne
(Remove QRM from my email address to write to me directly)

--- SoupGate-Win32 v1.05
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Antenna Man <kenpda@gmail.com> wrote:

I've been looking for a function generator app from which I can cut a >ringtone or notification tone that has the alternating 1336 and 1800
Hz IMTS "disconnect" tones that the IMTS mobile would send out to the
base when the mobile was 'hung up'. A second or two of it would play

Simple generation:

sox -V -r 48000 -n -b 16 -c 2 imts-disconnect.wav synth 30 sin 1336 sin 1800 vol -10dB

The file is on:

https://login.alphanet.ch/~schaefer/tmp/imts-disconnect.wav

You could then adapt the sox command line for your needs.

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Organization: Disgruntled Postal Workers Against Gun Control

On 2021-11-02 15:27:34 +0000, Marc SCHAEFER said:

Antenna Man <kenpda@gmail.com> wrote:

I've been looking for a function generator app from which I can cut a
ringtone or notification tone that has the alternating 1336 and 1800
Hz IMTS "disconnect" tones that the IMTS mobile would send out to the
base when the mobile was 'hung up'. A second or two of it would play

Simple generation:

sox -V -r 48000 -n -b 16 -c 2 imts-disconnect.wav synth 30 sin 1336
sin 1800 vol -10dB

The file is on:

https://login.alphanet.ch/~schaefer/tmp/imts-disconnect.wav

You could then adapt the sox command line for your needs.

Not quite. The tones alternate at 20 pulses per second, not
simultaneous. 1336 for 50ms, then 1800 for 50 ms, then 1633 for 50 ms,
etc.

***** Moderator's Note *****

I couldn't resist: I copied the "Organization" header into the text.

Bill Horne
Moderator

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Jay Hennigan <nobody@example.com.invalid> wrote:

You could then adapt the sox command line for your needs.

Not quite. The tones alternate at 20 pulses per second, not
simultaneously. 1336 for 50ms, then 1800 for 50 ms, then 1633 for 50
ms, etc.

Just once:

sox -V -r 48000 -n -b 16 -c 2 imts-disconnect.wav \
synth .05 sine 1336 vol -10db \
: synth .05 sine 1800 vol -10db \
: synth .05 sine 1633 vol -10db

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Jay Hennigan <nobody@example.com.invalid> wrote:

Organization: Disgruntled Postal Workers Against Gun Control

On 2021-11-02 15:27:34 +0000, Marc SCHAEFER said:

Simple generation:

sox -V -r 48000 -n -b 16 -c 2 imts-disconnect.wav synth 30 sin 1336
sin 1800 vol -10dB

The file is on:

https://login.alphanet.ch/~schaefer/tmp/imts-disconnect.wav

You could then adapt the sox command line for your needs.

Not quite. The tones alternate at 20 pulses per second, not
simultaneous. 1336 for 50ms, then 1800 for 50 ms, then 1633 for 50
ms,

You should be able to do that with sox too. Check the man page.

--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

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On Thursday, May 21, 2015 at 4:43:36 PM UTC-7, Bill Horne wrote:

Here's a trip down memory lane: does anyone remember the IMTS
systems that preceded cellular? I find myself getting nostalgic
for the "good old days" of the mobile world, and I wonder if
any of that equipment has been converted to other uses.

Here's an excellent site that covers both "MJ" (VHF) and "MK" (UHF)
IMTS Systems ...

http://www.wb6nvh.com/MTSfiles/Carphone5.htm

--
Bill Horne
Telecom Digest Moderator

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