My $5 swap meet telephone using a headset and a small keypad, just broke (headset). This unit gets all its power from the telephone line. I cannot believe how much trouble I am having getting a suitable replacement. All the headsets I have been able to find use the 2.5mm plugs to connect to a telephone. None seem to have the standard modular connectors that are, even now, used to connect handsets to telephones and telephones to wall jacks. So what is an old fuddy-duddy like me to do?
I did look around ebay before. Sometimes it is difficult to find things there even if they are there. "Telephone Handsets" found useless items. I then tried "modular telephone headsets." That found one vendor with many of the same kind to sell. There by be others, but I don't know how to find them.
That gets me to another question. The modular telephone connectors seem to be very reliable and widely used. Why have most manufacturers migrated from that to audio plugs and jacks?
It allows the manufactuers to sell custom items as a system and ask for higher prices (i.e. you buy their headset, you must buy their amplifier, etc.).
I used to work in the broadcast industry where 20 years ago all of this stuff was standardized. The headsets were made by Western Electric and used the dual 1/4 male mono phone jacks and plugged into the back of specially made telephones. These are still in demand today because they were made to never break, although you need to go hunting for them at a ham fest or maybe ebay.
Two years ago, I did buy a more or less generic handset amplifier at Radio Shack. It did come with a loop connection to the standard handset modular connectors and I used it with a Plantronics headset. I'm sure you know that the handset modular connector is different than the standard telephone line modular connectors on the back of your phone. It was kind of awkward to have all these cables on my desk, however. Plus, it needed its own wallwart power supply.
Unfortunately some of his "tech notes" are marketing blurbs!
Read the one titled "Loop Current & Circuit Loss Technical Bulletin" for grins and giggles. It is technically wrong in almost all respects. But he fills it with fancy words and lots of techie mumbo-jumbo to make is sound like something really important. The bottom line though, is that the basic premise is technically *wrong*, and the entire "Bulletin" is marketing hype designed to sell a worthless product.
The whole basis for it is bullshit. "High loop current" is not a problem!
Here are some great quotes:
"The carbon transmitter used in telephones ... needs over 20ma to sound good."
That might have been true in 1920... :-)
"Until about the mid 1980's, the big problem with loop current was that it was often too low. ... Now ... over 90% of the problems are high loop current. This is because the manufacturers of the "far end" pair gain equipment have adhered to a very old specification for loop current, but one that is still valid, that says between 23ma and 120ma are OK - but the CPE is much closer to the source of the talk battery than the old days. When the phone company tells you that they are within specs (while smoke wafts off your trunk cards at 80ma of loop current), they're right!
There is some truth there, though there was no "big problem" prior to the 80s and the symptoms identified for "now" are attributed to the wrong source. There simply is *no* problem with "high loop current". (Virtually all CO switches regulate line current at something between 27 and 45ma, depending on the switch.)
He fibbed a bit on the specs too. Loop current should be between 23 and 60 ma. The equipment however is supposed to be able to handle 120 ma, which is the absolute maximum under any circumstance that a loop current source should be able to provide.
You just won't find quality brand name telephone equipment that will provide 60ma of loop current, and you will be hard pressed to find quality brand name trunk cards that will burn out at less than 120 ma of loop current. (And if equipment does... is junk and should be replaced rather than apply some bandaid to hide the symptoms.)
He claims that resistors in trunk cards get hot and burn things, but in another place correctly says that telephone people don't like resistors in the line. There is a simple reason for that, which is why trunk cards *don't* have resistors in the line: A
300 Ohm resistor with 120 ma of current going through it has to dissipate 4.5 watts. For a 600 Ohm resistor that would be 9 watts.
That's enough heat to catch things on fire! Just imagine a shelf with 24 of those! *Nobody* puts that kind of resistance in series with a telephone line.
Another reason that his bandaid solutions are a poor fix for troubles is that in the other cases he then goes on to describe it is *not* excessive loop current that is causing the problem! His device just happens to also drop line levels by 2-3 dB, and
*that* is what is making a difference! He doesn't understand what is actually happening...
Here's another good one:
"At the end of a long loop, the current that left the CO at 35ma might be 18ma because of wire loss (resistance), and the audio level may be well below -8.5db, causing it to be hard to hear."
If there is 35 ma at the CO, there is going to be 35 ma at the customer too, absent a serious cable fault. I'm not sure how he picked out "-8.5db" (which I assume should be -8.5 dBm), as the design target is -9.0 dBm... plus or minus 3 dB.
The whole discussion of loaded cable is hilarious. This line is an example of the lack of comprehension:
"Data circuits have always been adjusted 13 db below voice levels (they like lines with low volume)."
That not true. Data circuits are not "adjusted" any different that voice circuits. The *average level* of data tones applied to the line is set to -13dBm0, and the reason is because that means the peaks will be just about exactly the same as voice peaks (which is to say, right at test tone level!). A bandwidth limited Gaussian distributed noise will have peaks at just more than 12 dB above the average signal level. That is what "data tones" are!
He used to have a whole diatribe on how modems would have high error rates if the loop current was too high. Most that that is gone now, but perhaps
has it if anyone wants to look. That used to be the main reason given for buying his devices. Of course the real effect was dropping the high levels (short loop... high current, but high levels too, and digital systems start clipping at 4 dB hot, so all it would take is a loop less than 1/2 mile long (3 dB hot right there) and any part of a connection, including the modem itself being a dB or so hot, and data rates plunge. Add just 2 dB of loss, and its back in business even if the only obvious difference is lower loop current).
I live in a really cool place!
Of course there are other parts of Alaska that are 1500 miles away from here. Some of those are pretty hot right now...
Asking what the weather in Alaska is like suggests you think it is a little island located between Hawaii and California, like they show on the TV weather maps. :-)
Actually, if we put Ketchikan down in Florida, I'd be up near northern Minnesota, while Adak would be in Mexico and Attu would be out in California. Dillingham would be in Oklahoma and Kodiak Island right on the border of Oklahoma and Texas.
(Anchorage is always Los Anchorage, even on that map.)
Here's a URL that show Alaska overlayed on the Lower-48.