atcomsystems.ca/forum Forums General General Telephone & Systems Information Whats the right thing to call it/what's in it?

Ah, If I just read before posting (From Arthur's wiki link):

"Many cell phones do not provide adequate sidetone. Usability experts believe this causes some people to shout or speak too loudly when using a cell phone. [1][2] Similarly, in military field operations in enemy territory, operatives can be encouraged to speak quietly by increasing the volume of the sidetone."

The goo is silicone compound. Earlier ones had some sort of black crap in them.

Circuitry like that is said to be "potted". It's used to protect the circuitry from water, moisture and tampering. That "black crap" was tar. Over the years many different types of potting compounds have been developed. The usual one today is a two part epoxy.

-Hal

Thanks Hal -

I'm just glad it wasn't PCB's..... and it sure kept me from tampering.

- Matt

Good topic for those without a proper telecom upbringing. As Arthur said the network is based on the hybrid circuit. They purposely make it unbalanced to provide the sidetone.

Matt, hopefully you will challenge us with qustions about queuing theory and nyquist sampling. You know that queing theory can be used to predict earthquakes, or the odds of obtaining a parking place.

Of course you all know my opinion about cell phones and their destruction of acceptible quality

I know about nyquil sampling... does that count? J/K.

Matt,

Nyquist states that you need to sample at twice the highest frequency to obtain a true representation. That being said, the phone system is based on transmitting bandwidth from 300-3300HZ where most power and telligable voice occurs. Some may say 3600HZ, but that neither here nor there. What really matters is that PCM circuits are at 8KHZ i.e. twice 4000Hz. 8 bit sampling at 8Khz gives you th 64kbps of a standard T-1 channel. Doing some math, 24 channels with this sampling rate + some signaling bits, gets you the 1.544 value.

Also that is why you see compact discs at 44KHz. Twice the highest frequency that one(not me) could hear.

And queuing theory?

Queuing theory is the reason that during a disaster when you pick up the phone you don't get dialtone.

I'm being simplistic of course, but Telephone Systems are built around the concept that they will NOT supply DT to everyone all the time.

It would just be too expensive

And the reason you can get away with it? Not everyone is (usually) on the phone at the same time.

Figuring out the right ratio of equipment (Trunks, DT registers, Time slots etc) to Telephone Lines is where queuing theory comes in.

It relies very heavily on statistical theories and practices. I did quite a lot of it when I ran the operation at the Bank of New York. Matter of fact when I took over as Network Manager it was probably 25% of my job.

An example:

You have one phone in your business - you need at least one line from the phone company. As you add phones and personnel you need to add more CO Lines, but not necessarily on a 1 to 1 basis. (Call Centers are the exception). The bigger your business gets the LESS CO lines you probably need as more and more of your business is carried on in-house.

At my location at the network hub of the Banks Private Network we had over 5,000 telephone sets. We had 180 DID (incoming) Trunks, about 180 DOD (outgoing) Trunks about 120 Long Distance Trunks and about 300 Tie Trunks to other locations on the network.

That's a ratio of less then 1 outside circuit for every 6 phones. We did have a very high ratio of time slots to extensions (24 slots for every 64 extensions) - that allowed for a high degree of internal calling.

Other sites on the network had similar ratios. (We had about 15,000 people on the private net).

Ask away. This is one subject I used to know quite a bit about. It should be a separate post though, probably under Telephone Services.

Sam

Cool. I can see how that would work. Then I guess you probably low ball it, and if the customer complains of having trouble getting a line, or grows, you just adjust upwards?

On the Carrier I was on, when in port, it was the inverse. 3,000 phones and probably 3 lines going out. Sometimes you'd spend hours trying to get an outside line. When at sea it was even harder.

Matt, same at Thule, Greenland AFB. Program called Morale Calls. Lines were available after 7PM local time to New Jersey, collect from there. Call the base operator and get your name on the list. Call might go through ANYTIME!
However, being in the sub-cable head bldg, we had access to allll sorts of options. Easiest was taking a morale call circuit for maintenance. But, you still had the collect charges. I used to get a spare channel on the Tropo shot patched thru to Cheyenne Mountain and then get an Autovon connection to Richards-Gebaur, then ask for off-base number XXX-YYYY. I quit that when I hung up, got a ring back a couple minutes later. It was the operator @ Cheyenne Mountain, wanting to know why they couldn't release the call. I call the Tropo shot @ Cape Dyer and had them tear down their patch, Tech control on base and had them tear down their patch and finally, tore down my patch. For all I know, that operator STILL can't release the call! John C.