Those Copper Wires Coming Into Your House - The Local Loop

It’s all going to be going away soon but, for most of us, our landline phones are still connected the way they were 80 years ago......

The analog Public Switched Telephone Network (PSTN) or Plain Old Telephone Service (POTS) local loop is defined as the twisted pair of copper wires many of us have coming into our home or business. This local loop is sometimes referred to as the “final three miles” or simply the “final mile”. The local loop has been “tuned” to our voice frequencies over the last 100 years and has a bandwidth of approximately 4000 Hz. This bandwidth includes two guardbands to prevent adjacent frequency interference. As can be seen in the figure below, bandwidth available to the local loop circuit for actual voice analog transmission is about 3000 Hz.

PSTN Bandwidth

The local loop wire pair consists of two wires and runs from a home or business to a Local Exchange Carrier (LEC) Central Office (CO) which is also referred to as the Central Exchange (CE).  The CO provides voltage (– 48V DC) for the telephone in our homes and businesses. The wires that make up a wire pair are identified as follows: The “tip” (red wire) is attached to the negative side of the CO 48 V battery and the “ring” (green wire) is attached to the positive side of the CO 48 V battery.

Local Loop Telephone Circuit

This diagram shows a basic local loop telephone circuit. Notice the CO provides the voltage for the telephone. This voltage is provided by batteries in the CO – we’ve all experienced power failures at one time or another and most realize telephones still work even when the power is out. Also notice the battery polarity is inverted and a –48 V DC is being provided to the phone. This is done for electrolytic corrosion reasons. In my next post we’ll look at the local loop in the form of a transmission line.

How Caller ID Works

Back in May I wrote a couple of posts using a book I published about ten years ago titled Introduction to Telecommunications Networks. As a follow-up to those basic telephony posts, here's something on Caller ID.

Caller ID, also referred to as Caller Identification Technology was introduced in New Jersey by Bell Atlantic in 1987 and became widely available in the United States with the implementation of a switching technology called Common Channel Signaling System 7 (SS7). I'll write about SS7 in a later post, for let's just say SS7 is necessary to provide Custom Local Area Signaling Services (CLASS). CLASS services include Caller ID, Call Return, Repeat Dialing, Priority Ringing, Select Call Forwarding, Call Trace and Call Blocking.

To transmit Caller ID information the SS7 system sends the telephone numbers of the caller and the recipient in the form of a signal to a transfer point, before the call arrives at the receiving end. The caller ID information, also referred to as the Calling Party Number (CPN) field is placed .5 seconds after the first ring between the first and second rings of a telephone call by the SS7 system in the transmitting central office (CO).

Caller ID or Calling Party Number (CPN) field

As the call travels over the caller to receiver route it may pass through network elements which have not yet been upgraded to SS7. If this happens the CPN information will disappear and the receiver will not be able to identify who is calling.

CPN information is delivered in frequency modulated digital data format. Simply put it’s a series of bits, or 1’s and 0’s, that are transmitted sequentially. The bits are organized into groups of 8, with each 8 bit group referred to as a Byte. Each 8 bit combination, or Byte, represents a letter of the alphabet, number or special character. In the CPN field a 1 is represented by a 1200 Hz tone and a 0 is represented by a 2200 Hz tone.

Let’s look at the layout of the CPN field in more detail.

Calling Party Number (CPN) field Detail

The message info fields include the type of information is included in the CPN field and how long (how many Bytes) the CPN field is. The variable length number field can include name and/or address information. Caller ID requires the use of telephone capable of displaying caller ID information or a display box attached to a non caller ID display phone. The receiver must wait for the time between the first and second ring to see caller ID information. If the receiver picks up the phone before the CPN information is received, there will be no caller ID information. This easy accessibility to caller numbers and other information concerns many people and has created a privacy debate.

The Constitutionality of caller ID has been repeatedly challenged in court. People have three major concerns: the right to be left alone, the right to be free from unreasonable searches or seizures and the right to not be subjected to unreasonable government intrusions. Call blocking has originated as a solution to this privacy problem. Call Blocking allows the caller to prevent their number from being displayed on the receiver’s caller ID unit. Caller ID can be blocked two ways. Per-Line Blocking blocks the callers ID from all connected telephones. Per-Call Blocking requires the caller to dial *67 prior to dialing any call for which the caller wishes to be anonymous. When a CPN is blocked, the telephone company replaces the CPN information with “Private Name Private Number” or something similar.

Massachusetts Broadband Institute Announces Grant Awards

The Massachusetts Broadband Institute (MBI) announced $335,000 in competitive grant awards today. These grants are part of  MBI's Last-Mile Broadband Solutions Program to advance last-mile solutions and expand broadband connectivity in underserved areas of Massachusetts - specifically in western and north-central parts of the state. Providers will use a combination of new technology and existing infrastructure to eventually tap into MassBroadband 123, the MBI's 1,338 mile Internet backbone network that will extend broadband access to over 120 communities in western and north central Massachusetts.

Here's more detail from the MBI website:

• The broadband planning grants were designed to fund the development of market studies, business plans, network engineering and designs, and other actions needed to develop and implement last-mile broadband solutions.
• Grant recipients were selected through an open, rigorous and highly-competitive process. 
• MBI funded broadband planning and deployment grants up to a maximum of $50,000 per provider and project, supported by a 25% funding match from the grant recipient. 

Here's details on the municipalities, broadband service providers and organizations that received grants today;

Broadband Planning Grants

• The town of Leverett, in collaboration with Crocker Communications, will receive $40,000 to plan a Fiber to the Curb network, serving all 640 homes in the community.
• The town of Royalston will receive $11,250 to design a wireless network to serve the community.
• The organization WiredWest will receive $50,000 to further develop their broadband network design and business model that will serve 47 communities in western Massachusetts.

Broadband Deployment Grants

• Mid-Hudson Cable, an Internet service provider, will receive $44,000 to deploy a wireless network to provide access to approximately 185 homes in the town of Tyringham.
• GAW High-Speed Internet will receive $40,000 to deploy a wireless network in the town of Ashfield to provide access to approximately 200 customers.
• AccessPlus will receive $50,000 to deploy a new wireless network to service 170 homes in Savoy and surrounding communities. 
• The town of Warwick will receive $50,000 to expand and upgrade its wireless network to reach 400 more unserved homes in town. 
• The town of Princeton, in collaboration with Ayatch Wireless, will receive $50,000 to expand its wireless network to reach 100 more customers.

Watch www.massbroadband.org for more information.

Google+ Project Takes on Facebook

Today, Google unveiled the Google+ project. It's similar to Facebook in some ways with some nice additional enhancements. One of the nicest features (which technically you can do with Facebook but it's not as easy to do) is Google+ allows users to create "circles" which are separate groups of people. Users can then post circle updates that members of that circle can see.

Another nice feature called "Hangouts," allows users to connect with friends using multiperson video.

Google+ can also be setup to automatically upload mobile photos into the cloud so you can easily move them from device to device.

Here's a short introductory video from Google on the project demo'ing some of the features.

Google+ is in limited Field Trial right now and is being tested with a small number of people. You can leave your email address here and they'll make sure you're the first to know when they're ready to invite more people. Get more information on the Official Google Blog and take a tour. 

I like what I see so far.

Have an iPhone and Kids? Then You’re Probably An iParent!

I’ve written here in the past about helicopter parents who are in almost constant contact with their older children using mobile devices but iParents seem to be taking things to a whole new level.

Retrevo.com, the consumer electronics shopping and review site, is running an ongoing study of people and electronics and then using this information to publish the something called the Retrevo Gadgetology Report. The most recent study,  involved over 1,000 online individuals in June 2011 and takes a close look at the use of social media by parents. Here’s some of the study highlights:

• 18% of parents say they feel like they couldn't stop using Facebook/Twitter even if they wanted to.
• 47% of parents of kids under 19 say they've used Facebook to learn more about their kid's friends.
• iPhone owning parents (iParents) are twice as likely (28%)  to get anxious when they don't check Facebook/Twitter as most parents (14%).
• Dads are more likely (13%) to use Facebook to learn about their kid's dates than moms (10%).
• iParents are twice as likely to use Facebook to learn about their kid's dates than Droid owning parents.
• Phone owning parents are four times LESS likely to have under 50 Facebook friends.
• 32% of iParents have over 250 friends (compared with 23% of other parents).
• Up to 34% of parents admit to using Facebook to check on their kid's friend's parents, by the time their children are between ages 13 and 19 years old.
• 12% of all parents feel they could not stop using Facebook and Twitter. This number more than doubles when looking at iPhone owning parents (19%).
• 11% of parents said they've given up activities they used to enjoy because they spend time on Facebook or Twitter. 18% of iPhone owning parents feel the same way (compared to only 12% of Droid owning parents).
• iPhone owning parents are twice as likely to get nervous or anxious if they don't check Facebook/Twitter (28%).

Pretty interesting stuff. Check out the June 2011 Gadgetology Report along with earlier reports linked here.

FCC Ups Caller ID Spoofing Penalties

I've written here in the past about caller ID spoofing - faking a voice caller ID to trick the receiver into thinking someone else is calling. Most recently last winter there was a rumor going around that Wisconsin Governor Scoot Walker's called ID was spoofed for a prank radio DJ call. In a post back in February, I said it was in fact illegal. Today, the FCC just upped the penalties for spoofing caller ID's. Here's some details from a post over at thehill.com:

• Caller ID "spoofing," can still be used for legal purposes such as safeguarding the privacy of individuals. But the commission argues spoofing is increasingly used for malicious purposes such as identity theft or placing false emergency calls to police.

• In compliance with the Truth in Caller ID Act signed into law by President Obama last year, the FCC rules would fine violators up to $10,000 every time they change their caller ID information with the intent to commit harm. The fine increases every day the violation continues up to a limit of $1 million.

You can get more information on the Official FCC Blog.

Comcast Deploying Upstream Channel Bonding

The  DOCSIS 3.0 cable broadband standard allows channels to be bonded (or combined) for higher data (Internet) bandwidth. Cable providers like Comcast have been testing upstream channel bonding for a while now with upstream speeds up to 75Mbps demonstrated in labs.

Looking at the DSL Reports Forum, it appears there has been some deployment randomly by Comcast in California, Florida and Indiana. I'll be watching for this at my home in Massachusetts!

Very nice!!