Mystery Circuit Board in Telephone Box

Thread Starter

mike4951

Joined Jun 27, 2018
4
Our local telephone tech removed this from our outside landline box. He said he had no idea what it was. Any ideas?
0.jpg
 

Dodgydave

Joined Jun 22, 2012
8,398
Looks like a Ctcss tone decoder, as used in Two Way radio comms, it transmits a low frequency audio (98 to 256Hz) over the phone for the decoder, to prevent listening in, so that it can transmit several conversations on one line.
 

xox

Joined Sep 8, 2017
351
Looks like a Ctcss tone decoder, as used in Two Way radio comms, it transmits a low frequency audio (98 to 256Hz) over the phone for the decoder, to prevent listening in, so that it can transmit several conversations on one line.
What would be the purpose of that for a landline connection?
 

Thread Starter

mike4951

Joined Jun 27, 2018
4
I would add that this is on a ranch a long way from anything. It appears to have a date (of mfg?) on the back of 03 87. I suspect its been there since around that time.
 

RichardO

Joined May 4, 2013
2,273
What would be the purpose of that for a landline connection?
I would add that this is on a ranch a long way from anything. It appears to have a date (of mfg?) on the back of 03 87. I suspect its been there since around that time.
Maybe to prevent the neighbors from listening in on the party line. ;):D
In reality, from what I found on-line, very few party lines still exist in the US.

Just curious... Where is the ranch (roughly)?
 

Thread Starter

mike4951

Joined Jun 27, 2018
4
Looks like a Ctcss tone decoder, as used in Two Way radio comms, it transmits a low frequency audio (98 to 256Hz) over the phone for the decoder, to prevent listening in, so that it can transmit several conversations on one line.
Here's an idea:

Maybe this was used as a way to have multiple phone users use the same physical telephone line - like an old time party line. As I said above, this ranch is in the middle of nowhere in Montana and this board is 31 years old.
 

Thread Starter

mike4951

Joined Jun 27, 2018
4
Maybe to prevent the neighbors from listening in on the party line. ;):D
In reality, from what I found on-line, very few party lines still exist in the US.

Just curious... Where is the ranch (roughly)?
Here's an idea:

Maybe this was used as a way to have multiple phone users use the same physical telephone line - like an old time party line. This ranch is in the middle of nowhere in Montana and this board is 31 years old.
 

Kermit2

Joined Feb 5, 2010
4,158
Phones were quite often "patched in" to those farm and ranch radio repeaters so wifes could send updates honey do lists.
That would also fit in with the dual tone encoder you found. Only radios with the proper decode board would unsquelch to get the transmission with that specific pair of tones. This way several users could share a repeater but not be bothered with conversation not specific to them
 

KJ6EAD

Joined Apr 30, 2011
1,568
At first I thought it might be a hybrid board to convert 4-wire service to 2-wire but based on when it was installed it may be a DTMF to pulse converter to allow the customer to continue using pulse dial phones when the central office facility upgraded to DTMF only. After that, any new phones purchased would be DTMF or support both modes by changing a switch setting on the phone. Twenty or thirty years later, all of the old pulse dial phones have been replaced with DTMF models and the converter isn't needed anymore.

The red coating is a dipped conformal coating to protect the circuit from weather, insects and fungus growth. You can throw the board in an outside-mounted network interface box and expect it to be reliable for many decades.

I had an elderly neighbor who still had a pulse dial phone in the early 1990s. It was owned by the phone company, as they were for most of the first century of phone service, and she was being charged a monthly fee for it's use. I clued her son into the situation and he got her one of those nice old folks phones with the big buttons, enhanced volume and all the kids' numbers programmed in.
 
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