"The phone is a remarkably complex, simple device, and very rarely ever needs repairs, once you fix them." - Dan/Panther
Started by bellsystem, June 26, 2017, 05:18:03 PM
Quote from: bellsystem on June 28, 2017, 10:43:10 AMSo far, analog has proven to be far more reliable in disasters and emergencies than digital.
Quote from: bellsystem on June 26, 2017, 05:18:03 PMI asked the following question on Stack Exchange but was told it was off-topic: https://networkengineering.stackexchange.com/questions/42193/pbx-co-trunks-analog-multiplexing-analog-version-of-priIt's sort of technical in nature which is I presume why it was put on hold.Does anyone know if they can maintain an analog connection between the central office and their house/business using just 1 cable, like PRI, but with analog channels instead of digital? Is there a name for this type of technology to distinguish it from PRI?I want the call quality and reliability of having as many separate landlines coming into the building as I needed outside lines, but the convenience that one large cable coming in offers - in addition to one cable, Direct Inward Dialing and Direct Outward Dialing are my primary concerns.Nobody on the site I posted to was helpful, so thanks in advance to anyone who can help me out with this!===========================================EDIT: text copied from "other site" and pasted here for posterity"PBX CO Trunks: Analog multiplexing (analog version of PRI)? [on hold]I've been doing more research into PBXs, specifically trunk connection methods. My understanding is that there are 3 primary options: Separate telephone lines for each trunk line Primary Rate Interface (PRI) Session Initiation Protocol (SIP)I'm trying to figure out what the best way would be to connect an analog-only PBX to the central office. I've already ruled SIP/VoIP out as being considerably inferior, from a quality and reliability perspective especially. PRI is preferable to SIP, but my understanding is that PRI uses TDM/digital transmission which would not be acceptable.- - - - - - - - - - - - - - - - - - - - - - - - - -Premise: Transmission must be analog, not digital, for call quality and reliability - the call quality should be basically the same as that with a separate standalone landline connection. Digits should be dialed immediately. I know many systems "hold" digits and then analyze the digits dialed using a "dial plan". Internally, this might be of some used. But if "9" is dialed for an outside line, I want the PBX to grab an outside line for the station and step out of the picture. The digits should be sent to the central office then as they are dialed, not all at the end (again, as with a separate, standalone landline connection). Going along with my second point, all central office connections, whether they are individual cables or one large one with separate analog channels, would have to be identical. Because the circuit will be grabbed as soon as "9" is dialed, all "features" (i.e. ability to make Long Distance/International calls) would have to be the same for each line/channel, since it would be impossible for the actual intended number to be analyzed. Basically, the call should be being routed as it is being dialed, not after. There's extreme controversy it seems regarding 9-1-1 and 9 9-1-1 going around (the linked petition will be impossible to force for systems such as the one I desire). I know that 9-1-1 will not be doing anything because to the central office, it looks like 1-1 has been dialed which could have easily been a switchhook mishap (I assume this is why 1-1 is not rerouted to 9-1-1). The PBX will be in a home environment (not a public system) and since I, most of the time, will be its only user, I will know to dial 9911 instead of 911 anyways. 911 should NOT connect to anything. I don't believe nesting PBXs will be a problem. I am going to buy a PBX that will support at least 50 stations, but one of the "stations" will end up being a corded switchboard PBX (PMBX or Private Manual Branch Exchange), and other "stations" may be other sub-PBXs that are PABXs, like the main one. Is there any way to use features like Direct Inward Dial from telephone stations to PBXs nested further down in the tree?- - - - - - - - - - - - - - - - - - - - - - - - - -I'm trying to figure out which networking technologies would best meet most, if not all, of my requirements. My guess is it would be some technology that lies between separate regular landlines and PRI, if there is one. The PBXs that will actually be used are arbitrary and irrelevant, but they will all be analog and have no digital support.I believe something along the lines of an early 1970s analog PABX would end up being used (as is described here), but I am interested in what transmission technologies concerning the trunk lines should be used.Is there a sort of medium between separate analog lines and PRI? I'm looking for a medium that will retain an analog transmission between the PBX and the Central Office, but the switching technology itself can obviously be digital (as all PABXs are). Is there any way to maintain an analog connection between the central office and the PBX without running separate regular landlines for each trunk? Analog will be needed to support good call quality for regular analog rotary and pushbutton phones, fax machines, and modems (including dial-up). I want whatever trunk technology is used to function like a standalone line without actually being 4 or 6 separate standalone lines. Costs aside, my primary concern with having standalone lines will be direct inward dialing as well as direct outward dialing. Even if there are 50 stations, there are only a few numbers I'd want to have DID and DOD for - otherwise, I want only ONE telephone number - and NOT as many numbers as there are trunks (this might be appropriate for a Key Telephone System but not a PBX), since I want one number to be used for Caller ID from any non DOD phone, which I don't think standalone lines would support.If my internal extensions range from 1000 to 1500, the numbers I need supported for DID/DOD would be 1000 as well as a few other numbers between 1000 and 1200. I don't want to have to purchase a whole block of 200 "numbers" if that can be avoided (unless there is no additional cost).I am estimating between 4 and 6 trunks will be required. Costs are not a concern, although since this will be installed in a home environment with 1 bill-payer, ideally they should be low.Summary: No digital transmission (i.e. packet switching) Analog multiplexing is possible so multiplexing is fine if each individual circuit is analog. Routing as calls are dialed, not after Compatibility with DID and DODCLARIFICATION: I'm not asking anything about a PBX at all. I'm inquiring about the protocols used, specifically PRI, and if an analog variant of PRI (possibly a predecessor to PRI) exists."
Quote from: bellsystem on June 28, 2017, 05:31:32 PMI'm not confused.As long as the distortion introduced into analog transmissions is less than the loss of quality that is inherently going to be produced when a digital sampling is taken of sound, which is INHERENTLY ANALOG... then analog will be superior.Sounds like everyone here is dissing analog because of DISTORTION and DISTORTION only.Maybe someone in the PSTN should consider using SHIELDED cabling to minimize distortion. Shielded analog would definitely be better than digital.As it stands, digital was introduced for long-distance mostly because of cost. It was so much cheaper than to use microwave radio relay and digital cabling for long-distance calls so one cable could have many calls going across it.If we ignore cost and focus on the fundamental qualities of the two transmission methods, sound is NATURALLY ANALOG and will be closest to its purest form if KEPT analog. When sound is converted to digital and then back to analog, the actual audio/sounds that were produced at the other end are NOT reproduced accurately.
QuoteIf you want your own circuit-switched central office with battery, I would suggest an Option 11 PBX with analog line cards and it has battery backup, will accept rotary dial, digitone, Autovon, ISDN ksets, and Meridian phones. It will satisfy your needs. Very nice small switch. You can do 7 digit dialing, and you can use the Universal Analog Trunk Card, although I recommend the PRI.
Quote from: bellsystem on June 28, 2017, 07:13:36 PMDigital is not a truthful exact regeneration. By definition, as soon as something analog, like SOUND, is converted to DIGITAL, it is no longer the EXACT same sound wave (oh wait, it's not actually a sound wave at all).
QuoteIn order for digital to be on par with analog when it comes to accuracy, distortions aside, the sampling rate would have to be INFINITY, which is, of course, impossible.That's why analog is used. No such thing as sampling rates, since they're irrelevant. It's just a constant connection that literally transmits audio, not 1s and 0s of the audio.Digital may sound better in the send in many cases but analog is a more ACCURATE reproduction of the original sound wave, since it IS that sound wave.
Quote from: unbeldi on June 29, 2017, 10:09:46 AMEVERY communication system has to make compromises between physics, economics, and policy or politics. Your ideas about infinite sampling rates to achieve analog quality is simply wrong, because no transmission channel exists that has infinite bandwidth, that can transmit messages without loss or distortion. A perfect channel is exactly as impossible as an infinite sampling rate.