skipp025 wrote: > Who reported they passed tests? The phone company promise the > moon report... or did someone other than the phone company > actually check them at least for loss and hf roll-off? You can > bet the actually line impedance is probably not close to 600 > ohms unless you verify/test it. Rare do I believe what I'm told > without minimal verification done someone on my side of the job. > > I had the inductive interference group come out and verify the readings. I watched while the test was done with a Sidekick 7B T&N tester. The circuit is within specs for noise, I did not do a frequency run test yet. > > How are you dealing with the two terminated remotes across one > line? > > > I'm bridging the three circuits together for lack of any other solution. The telco radio circuits were ordered as separate circuits, so it is up to the customer (now me) to figure out how to bridge them together. Keep in mind that I stepped into this midstream, so I'm trying to make the best of it with limited funds. > Not really in all cases... do you know the frequency of the/any > hum you're hearing? It's a clue as to the source of a problem. > Are you hearing hum/buzz from one particular line? or the > combination of the local and distant remotes? > > 60Hz AC hum, but keep in mind the circuits are within specs. Once I balance out the audio I should have a good S/N ratio and the hum will be negligible.
> You could wire transformers in a number of schemes... just > paralleled, as a hybrid or using different secondary values... > into a custom interface. > > I just pulled the manual for the CPI TR Series Tone Remote and > it has true physical transformers in place... so you should be > able to interface all the remotes without a problem without a > bunch of extra stuff. I know it's a pain, but you should probably > find and deal with external to the equipment problem generators. > The transformers that are in the CPI TR10 are at remote locations. I'm talking about putting isolation transformers at the Remote Base source side of the circuits. The only time the hum becomes a problem is when all three remotes are tied together. That's why I'm trying to get some isolation between the circuits. I can't give this trouble back to the telco because the two radio circuits meet spec when tested individually. What I'd like to find is a 3 to 1 bridge to connect them together. That way, each remote would be terminated and the individual remotes would have balanced impedance. Many years ago, at my bell system testboard job, this would be the solution. Each circuit would be terminated at 600 or 900 ohms at each end and isolated from each other. The losses incurred would be made up with amplifiers. Joe
