I recently heard a term for a regular tel line. For example a line I would use for a fire alarm panel as opposed to a line connected to a PBX or whatever. I want to use the term but can not remember what I heard. It was sort of like plain old tel line. It may have had an acronym. Any one know hwat I may have heard?

Back in my telecoms days, we called it Plain Old Telephone Service, or POTS.
We also had Pretty Advanced Network Services, PANS.

Thanks.
POTS may have been it.
I wrote it down when I heard it and as usual have no clue where I wrote it down.
It is probably what I heard but it does not really fit how I thought I could use it.

POTS is the only term I can think of off-hand which has this slightly tongue-in-cheek air about it.

I designed an installation of some high tech medical equipment just last year and found "POTS" listed as a requirement for their site preparation in the manufacturer's manual.
The manufacturer said that they ran into issues whenever they went through the facility's phone switchboard and wanted a direct outside line or a POTS (Plain Old Telephone System); so I suppose that the dumb sounding acronym has been officially blessed by the high tech gurus of the world.

It really is the accepted industry-standard term. Even an order taker at the telephone company's business office will immediately recognize this term.

The reason that many equipment manufacturers require a POTS line is to avoid the need to dial additional digits in order to get an outside line (9 for example). Also, line voltages vary greatly on various PBX or key systems. The manufacturers want to see uniform voltages which are supposed to be present on POTS lines. They rarely are any more.

Annother less common (though I believe more correct) acronym is PSTN - public switched telephone network.

Yes, this is a commonly-used acronym for the telephone network itself, but not for an individual line.

The regulation agencies and telcos in Ireland tend to call it PSTN (Public Switched Telephone Network) service when referring to normal phone service. POTS seems to be more of a casual way of describing it.

Terminology we use:

PSTN - Public Switched Telephone Network
ISDN - Integrated Services Digital Network
xDSL - Any form of Digital Subscriber Line service.
VoIP - Voice over Internet Protocol.

I realise that PSTN can also be used to describe the entire telephone network//