Private Lines
About Private Line

Private Line covers what has occurred, is occurring, and will ocurr in telecommunications. Since communication technology constantly changes, you can expect new content posted regularly.

Consider this site an authoritative resource. Its moderators have successful careers in the telecommunications industry. Utilize the content and send comments. As a site about communicating, conversation is encouraged.

Writers

Thomas Farely

Tom has produced privateline.com since 1995. He is now a freelance technology writer who contributes regularly to the site.

His knowledge of telecommunications has served, most notably, the American Heritage Invention and Technology Magazine and The History Channel.
His interview on Alexander Graham Bell will air on the History Channel the end of 2006.

Ken Schmidt

Ken is a licensed attorney who has worked in the tower industry for seven years. He has managed the development of broadcast towers nationwide and developed and built cell towers.

He has been quoted in newspapers and magazines on issues regarding cell towers and has spoke at industry and non-industry conferences on cell tower related issues.

He is recognized as an expert on cell tower leases and due diligence processes for tower acquisitions.

« August 2005 | | December 2005 »

September 23, 2005

Email: H. Daehne

Hendrik Daehne is a computer science student at the University of Hamburg. He's currently writing a paper about security issues in C450 and AMPS for his network security course. I thank him very much for contributing these hard to find details about Germany's C-Netz.

Hi Tom,

Great site!

I just saw your table about "Analog or First Generation Cellular Systems". ( http://www.privateline.com/PCS/history9.htm ) I can offer you some additional information about "C-Netz": "C-Netz" or "Netz C" is German for "network C" and stands for the third mobile phone network (succeeding the networks A and B) of the country. The German C-Netz was based on the C450 technology, the Austrian C-Netz on NMT450 (hence, the table is not correct about Austria).

C450 was developed by Siemens around 1980. It was -- to my knowledge -- the most advanced analogue system in the world. Some of its features included non-audible in-band signalling (using analogue audio compression with data bursts in the resulting time slots), speech scrambling (band inversion) and incoming and outgoing waiting queues for when the network is congested. Signalling was completely digital (no tones like SAT).

The German network started with magnetic stripe cards in 1985, followed by memory chip cards in 1988 and eventually by microprocessor chip cards in 1989. These microprocessor cards had a phone number memory and could be used with public card payphones (billed on your cellular account). They also introduced security features like PIN codes and authentication (using challenge-response algorithms). As you've already mentioned on your site, the nearest cell tower was determined by signal delays rather than by field strength (the system supported both ways). For this purpose the network was completely synchronized.

The network in Germany started trialing in 1985, and was launched
commercially in 1986. It reached around 800.000 subscribers in 1993.

The networks in Portugal (1989) and South Africa had much lower customer numbers. All networks were shut down around 1999/2000. Subscriber equipment providers included Siemens, Alcatel, AEG, Philips, Motorola and Nokia.

The phone I attached was developed by Technophone in the UK, but sold under various brand names starting in 1988 (the images are from flyers released by "DeTeMobil GmbH", which are now known as "T-Mobile Germany").

Greetings from Hamburg/Germany,

Hendrik

[Picture One] [Picture Two]

September 16, 2005

Hardware Warriors

Excellent article below. Read the whole piece before it is pulled off the web:

Hardware Warriors

An unusual link to Silicon Valley's cultural and technological history, the Electronics Flea Market is practically a subculture in itself

By Russell Mahakian

IF ONE MAN'S JUNK is another man's treasure, then the trucks and vans arriving before daybreak at De Anza College's parking lot for the Electronics Flea Market are carrying either cabs full of garbage or mechanical wealth beyond a gearhead's wildest dreams.

A novice may be left dumfounded by the bins overflowing with metal machines, some with '50s sci-fi knobs that look more like props from Forbidden Planet than devices with any practical use.

Look closer, though, and you'll find a hands-on history of electronics and technology in Silicon Valley. Browsing through boxes of old gear and electronic cables provides a clear view into the innovative thinking and social scene that made this valley ripe for a tech explosion.

"This stuff was our Super Mario Bros. There is real history in this stuff," says one flea market regular, pointing to a Heathkit mulitmeter.

(continues here, external link --->)

September 13, 2005

Learn to Repair Cell Phones

Q. Where can I learn to repair cell phones?

A. Tom Farley here. There isn't anywhere to learn since most aren't repaired. Cell phones now use surface mount components, which means parts can't be easily replaced from their circuit boards. The days of discrete components are long gone. Also, since the price of cell phones is so low, they have become disposable, even with the most expensive models. It's cheaper to ship the customer a new phone. What carrier wants to take in an old phone, ship it to the manufacturer, have Samsung or Motorola chase down a defective transistor or diode, replace it, put the phone back together again, and then ship it back? Geoff Fors contributes the final word:

"Well, you are right. Cell phones are disposable. Most are manufactured in China on robot machinery and most of the parts are not available here anyway, nor are the schematics and technical diagrams. There is no provision whatever for repairing them anymore. The last phones that anybody tried to offer repair on were the Motorola 'Flip-Phone' Micro-Tac models of 1987-89, and those had to be shipped to Motorola for service. That's why you'll find trash bins at Office Depot and elsewhere with signs on them saying 'deposit cell phones and empty printer cartridges here.'"

"Two way radio repair is a dying art. That's why so many truly wonderful two way radios are for sale on eBay for $5 to $10. There is no one left in the industry to repair them or understand them. They just change modules or boxes. PG&E in California closed down its radio repair shops back about1992-93 and today just ships the whole thing back to the manufacturer, which is the wave of the future. So many businesses have dropped two way use in favor of Nextel handsets that there isn't much business left for traditional two way. They are now paying the price for that in Louisiana and Mississippi where nothing worked (or works) when it was needed the most."

"I recently saw a job ad on one of the newsgroups I subscribe to, for a radio shop supervisor with Texas D.O.T. in Wichita Falls. They wanted someone to be a one-man-band familiar with everything from computers through microwave multiplex including component level service, preferably with a college degree, yet they wanted to pay 'about' $ 2500 per month. That's another reason nobody wants to get into the radio communications business. Considering that it was a salaried position without overtime, I expect the guy will be working for about 3000 hours a year, which works out to $10 an hour before taxes, less than many unskilled labor jobs. There's no future in civilian radio repair."

September 10, 2005

Ambassador Hotel 1968 Switchboard

Q. Would the Ambassador Hotel in Los Angeles used a switchboard in 1968 for its incoming and outgoing telephones calls to connect to the rooms?

A. (Tom Farley) Most probably, yes, they would have had a manual switchboard well into the 70s. Computerized telephone switching for companies was still quite expensive at that time. And the lack of personal service would have been a strike against the equipment at a first class hotel. That's my best guess, I would be amazed if this wasn't true.

A. (J.R. Snyder Jr.) (internal link) The first paid job I had was working at the Scottsdale Hilton when I was 14, answering the manual cord switchboard for a few hours after school. My mother was the front offfice manager. They needed help while people were checking in, I got paid something like 50 cents an hour.

About four years later, around '73 or so, I was already at the phone company and my mother had become the General Manager (quite a coup for a woman) of the entire property. The hotel, owners, management, staff and regular guests, were in quite a tizzy about the old switchboard being taken out.

They were replacing it with a direct to the rooms PBX {private branch exchange, ed.] and it was sort of like them taking exchange names away. A lot of people thought it was impersonal. My mother's point of view was pure business (my mother is English and has little romance for these things) and thought the whole uproar was ridiculous. She didn't have to pay two switchboard operators and time and charges were automatic and almost indisputable.

I remember Zsa Zsa Gabor being cheap, cheap, cheap. She demanded flowers and fruit baskets (gratis) and denied every call she ever made and they just wrote them off to get her out of the lobby. The hotel Bob Crane was murdered in, which was pretty classy at the time, was about a mile away.

I do remember as a kid when we travelled a lot hating to have to use the phone because you had to go through a switchboard operator who KNEW you were "that kid" in XYZ room with his parents.

September 07, 2005

GSM Voice Traffic

Q: In GSM, does voice traffic between mobiles in the same cell site pass through the MSC? I'm not concerned about signalling information.

A. (From different contributors) GSM routes all calls through the MSC, just like AMPS (internal link). That's not the case with CDMA. Not surprising -- technology evolves, and IS-95 (CDMA) is newer than GSM. In the same way, UMTS, evolved CDMA, came after IS-95 and hence operates more like IS-95. Again, not surprising.

In a CDMA network a call as you describe would not route through the switch. Any calls going through the switch must pass through the vocoder to be converted to ordinary landline type voice traffic. Every time we do that, we lose quality, of course. Therefore, for a mobile to mobile call in the same BSC, the voice traffic does not route through the switch, but instead is simply routed to the other mobile so the voice doesn't pass through the vocoder any more than necessary.

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