Single tone Burst question

[firedog359]

Hello everyone.I am a Firefighter/EMT and my hobby is collecting vintage public safety equipment.I have recently started collecting vintage radio equipment and through another thread I was able to identify a couple of pieces that I had no clue about.The units are T-1398AM 2 channel DC remote control conselletes.They were used from the 60's-80's.These have the single tone burst function.I know from my research that this was the predecessor to CTCSS.Instead of a sub audible tone transmitted with the carrier to break squelch,a single tone burst was transmitted at the beginning of every transmission and whatever radio group was being called would decode the tone and break squelch and then the carrier would take over.This system was also used to access different repeater locations.While researching this I found a couple of companies producing new STB encoder/decoder boards and notch filter boards.What applications are still using this old technology ?

[Bill_G]

None that I'm aware of, but doesn't mean that someone somewhere isn't using it. Motorola marketed single tone as Auto-Mute, though we referred to it as auto-puke because the tones were not exactly precision generated, and often sounded more like the cat when you stepped on its tail. The tones were only generated on the first PTT to open up all the other rcvrs. The circuit was reset when you hung up the mic. If you were accessing a rptr, the first tone caused it to run csq, and it remained open until you sent a second tone by hanging up the mic. Simple system. Reasonably reliable. But, the tone could blast you out of the truck too. People didn't really miss it when they went to sub-audible ctcss tones.

[com501]

I use 1550 on my ham repeater just to annoy people who don't have tone burst encoders.....

Seriously though, it's been years since I have heard a repeater using it. The last folks that I can recall was the Secret Service.

[k2hz]

As I mentioned in my reply to your post about the console, I have never seen single tone used and I have been involved with 2-way since 1962. The odd thing about your console is that is specifically for control of a PL base with the optional current generator to provide the reverse current monitor function. The other function of that board is for second receiver mute but there is no mute switch on your console.

The combination of the single tone encoder and PL monitor is unusual. I would suspect the system had a heritage of single tone that was being migrated to PL when the console was used. The alternative is a single PL system with multiple repeaters selected by single tone. Multiple PL capability was not an easy option back in those days. Radios required a Vibrasender/Vibrasponder for each PL tone and DC remotes could only do F1/F2 unlike the multi-function capability of tone remote. You could kluge a DC remote for extra functions with the reverse current if you gave up the monitor function.

[Astro Spectra]

A single tone burst was often used to whistle up (activate) a repeater in the early days of FM. It was nicknamed whistle up because some people with good pitch could literally whistle the machine on.

In Europe hams still use a 1750 Hz tone burst to first activate their repeaters which then remain operational to stations without the tone burst facility for ten minutes or so.

[Will]

Single Tone was and may still be used to select which repeater is accessed in a multi repeater system.
The repeater responds to the correct single tone AND correct PL tone.

Used mostly due to mobile and base radios not having but one PL built in. So a single tone encoder was added.


Now a days most radios can have more than one PL in them, so which base or repeater to access is a mater of a Mode in the radio.
You had to be back there then to be in awe of those systems,

[Astro Spectra]

Brings back memories of MTS and IMTS...

[Bill_G]

Brings back memories of MTS and IMTS...

I used to make a box called ChannelGrabber for IMTS users.

[Astro Spectra]

Would it send a connect tone as soon as a free channel was marked idle during busy times?

[Bill_G]

And more!

[firedog359]

As I mentioned in my reply to your post about the console, I have never seen single tone used and I have been involved with 2-way since 1962. The odd thing about your console is that is specifically for control of a PL base with the optional current generator to provide the reverse current monitor function. The other function of that board is for second receiver mute but there is no mute switch on your console.

The combination of the single tone encoder and PL monitor is unusual. I would suspect the system had a heritage of single tone that was being migrated to PL when the console was used. The alternative is a single PL system with multiple repeaters selected by single tone. Multiple PL capability was not an easy option back in those days. Radios required a Vibrasender/Vibrasponder for each PL tone and DC remotes could only do F1/F2 unlike the multi-function capability of tone remote. You could kluge a DC remote for extra functions with the reverse current if you gave up the monitor function.

Along with the consoles I picked up a convertacom with an MX360 installed.It has 5 channels marked for different agencies and only one PL.These came from a very rural mountain county here in NC,so would there maybe have been multiple repeaters located around the county and the one closest to the dept or unit being contacted toned open ?

[k2hz]

Brings back memories of MTS and IMTS...

I used to make a box called ChannelGrabber for IMTS users.

I worked for an IMTS carrier and we upgraded to a Glenayre terminal with anti-ChannelGraber firmware much to the consternation of a vendor whos users phones now had great difficulty connecting.

The ChannelGrabbers had been really messing up the system stepping on each other or legitimate user connect attempts so that neither connected.

This is really OT to single tone burst so maybe we should start a thread about old signaling systems. Secode was my favorite LOL.

[Will]

Step and Fetch!