sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Telecom Service & Providers line measurements

i need to check a phone line. if i remember right on hook volts is about 50, and about 15 v off hook. and im thinking the loop current is about 25. can anyone help me stay on track. thanks dave

i didnt mention the reason. customer says the fax misses a lot of calls and tel co says the line is ok and fax manufacture says its the line. im in the middle and going out there thursday. they did replace the fax machine. thank dave

Sandman has a pretty good troubleshooting guide here https://www.sandman.com/trou-bul.html with the values you're looking for

I doubt you'll find anything. Fax just doesn't play nice with the digital world and VoIP that all carriers use at some point to route calls. That's what the manufacturer is telling you when they say it's the line. Sometimes slowing the fax transmission down through the settings (I've noticed recently some machines actually have a VoIP setting) will help. But in reality fax is old technology, a relic of the past. Scanning documents and email is the way things are done now and a scanner is cheaper than a decent fax machine anyway.

-Hal

What you want to remember is that telco will always tell you the line is ok. Back when I was a young sprout the local testdesk test was always line t-ok insp.we'd go out and the trouble would be in the CO, this saved them 5 codes (a form of measurement), 1 day they sent me in for vacation reliefe I lasted that 1 day because of the 5 codes I generated by not dispathing to the field.

One thing about fax documents, they are a legally binding document. You can fax something needing a signature to someone, they can sign it and fax it back and it's binding.
Unless things have changed, scanned documents are not binding.
So... I don't suppose faxes are going away soon.

The last thing I would do is replace a fax machine. That's the expensive last resort. Install the suspect fax machine on a real telephone line, either at the same premises, or a different place (like a neighboring business or your house) See if it will receive faxes. Then tell the phone company what you did.

You don't tell us what type of dial tone you're using. If it's VoIP then forget about it. They are not phone companies, and will not have any idea what you're talking about, nor are they obligated to do anything about it, since they are unregulated.

What do you mean by "misses" calls? No incoming ring? Incoming ring, but trips prematurely? Rings, gets answered, does not hear CNG? Hears CNG but won't send handshake? Sends handshake, but sending machine won't send fax? Gets faxes, but the page is garbled or blank? Some calls work, but others from different sources do not?

Line voltage and current will generally not adversely affect a fax call, unless the current is way up past 45 mils.

Not true. A faxed and a scanned pdf document are equally valid if they are valid at all. See here.

-Hal

On Hook Voltage -48 VDC; Off Hook Voltage -8 to 12 VDC. The BellCore spec for line current is 25-35 ma. That is what USED to be golden. Today, it's whatever the telco wants. Evidently, there are no more standards. (I know there are standards, it's just very few telcos are abiding by them.)

Case in point: Two customers. Two HP FAX machines, both new, both identical. One customer in Verizon territory had voltage right on the money, but current was 50 ma and the line loss was +6 db. His office was across the street from the CO. Verizon argued, over the phone, that the line was OK. Finally, after annoying them several days in a row, they finally sent a tech. He made the startling announcement that the line current was way too high! Amazing. He basically said he could put some resistors in line to help lower the current. I said I would put a Sandman regulator on the line which worked perfectly.

The other client is in Windstream territory. Line Voltage On Hook -89VDC. Off Hook -20VDC. Line current 45 ma. After 16 calls and three Windstream tech visits to the site, Windstream insisted it was the FAX machine. They claimed there is NO "standard" that they have to meet. It's, basically, whatever they provide. I tried to condition the circuit with Sandman devices and got a 75% completion of FAXs. The client has a Mitel, so I took a single line port from the Mitel and installed a LS/GS CO Card in the system and hooked the line through Sandman's devices to the Mitel. The FAX completion is 99%. I measured the line noise and it was in the red on my Tripplet. My Dynatel just said BAD LINE. So, I assume the 1% failures are due to a too high line noise.

Today, it's up to us to fix the telco's problems. They just don't care about specs and, often, don't know what I am talking about when I mention BellCore. Things sure have changed from when I worked for Mother.

Rcaman

Telcordia, the old Bellcore, now sets the standards. I doubt if many of the phone company's use or follow these standard and good luck trying to get a copy for yourself. They are not free documents.