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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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Headsets for cordless phones
A week ago I received a GE cordless phone and a Plantronics M110 headset
which I had ordered by the internet. The phone has better range and clarity than my old one, and the headset sounded great on my first conversation. Since then, I have discovered that for most conversations the headset is not as good as listening to the phone itself. It sounds like an impedance mismatch. The input impedance for the M110 is 32 ohms, but GE doesn't seem to publish the output impedance for the phone. The Plantronics box says the headset is for mobile and cordless phones and will provide crystal clear conversations for most headset-ready phones. When I contacted them, they said the M series is not recommended for 2.4GHz or DSS phones. Doesn't at least one of these apply to most headset-ready cordless phones? They recommend their H51N with an adaptor cord. I paid $20 for My M110, while the H51N lists for $100, and I'd still have to find an adaptor. I wanted a headset to make calls when I'm likely to be put on hold and for incoming calls when I'd like to continue manual tasks. It would be worth $20 to me but not $120. It would have saved me some trouble if their advertising hadn't led me to believe they recommended the M110 for my phone. Besides price, the difference between the two headsets seems to be impedance or the earphone. I think the H51N is 150 to 300 ohms, but I haven't seen it published. There's probably a suitable headset available for less than the H51N, but vendors of cordless phones and vendors of headsets tend not to mention impedance. How can a consumer match the two without knowing impedance? If I can't get specs for headsets, I might get specs for microspeakers, to replace the one that came in the M110. For example, I've seen a 100-ohm microspeaker advertised for $2. What should I do? -- Best Regards, Lloyd |
#2
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Headsets for cordless phones
In article ,
"Clifton T. Sharp Jr." wrote: Lloyd Randall wrote: It sounds like an impedance mismatch. The input impedance for the M110 is 32 ohms, but GE doesn't seem to publish the output impedance for the phone. The last GE phone I bought came with its own headset; it was 150 ohms. I suspect your phone might be as well. Natch, no headset worked with my phone when the supplied headset broke; VERY low earpiece volume. If a earphone were a resistive load, it would simply be too soft if the source impedance were too high. In fact, earphones have mechanical resonance at various frequencies. The higher the source impedance, the louder these frequencies will sound, relative to other frequencies. The output will wound harsh and distorted, and it will sound unclear because some frequencies will be very soft. With the GE phone, my M110 is harsh and unclear with some voices. I think those are the voices that are strong in the frequencies where the earphone resonates. Telephone-line impedance is nominally 600 ohms. That would explain why telephone headphones use to be at least 150 ohms. Earphones for lightweight aviation headsets are nominally 600 ohms. I think the walkman was responsible for the popularity of 32-ohm earphones; with two penlight cells for a power supply, you couldn't get loud music if the earphone impedance were much higher. Is 32 ohms standard for cellphone headphones? If so, it may be because walkman earphone elements were readily avialable. If cordless phones don't use the same headphone impedance, could it be because manufacturers don't want customers buying cheap cellphone headphones for their cordless phones? There must be inexpensive 150-ohm headsets or earphone elements available. If only specs were easier to find! -- Best Regards, Lloyd |
#3
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Headsets for cordless phones
In article ,
"Clifton T. Sharp Jr." wrote: Lloyd Randall wrote: "Clifton T. Sharp Jr." wrote: Lloyd Randall wrote: If a earphone were a resistive load, it would simply be too soft if the source impedance were too high. In fact, earphones have mechanical resonance at various frequencies. The higher the source impedance, the louder these frequencies will sound, relative to other frequencies. The output will wound harsh and distorted, and it will sound unclear because some frequencies will be very soft. I have loud tinnitus; the volume was too low for me to detect distortion. It was low enough that I could barely detect speech, and too low to hear what was being said. I hear you! The phone I replaced was another GE cordless. It had become so faint that I'd shut off all noise sources and jam the phone hard against my ear, but I'd still have trouble understanding what was said. Even if all phones had microphones with the same gain, some voices would be faint because people let the mike get too far from their mouth. Some of the faintest are in customer service. The first time I tried my headset, I walked around outdoors to see the range of the cordless phone. The man I was talking to said he knew I was near the limit of the phone's range because he kept hearing pulses of hissing as I moved around. I never heard them until I tried the phone without the headset. I guess the impedance mismatch made those frequencies too faint to hear in the headset. Overall, my headset sounded reasonably loud (but not clear and pleasant) because resonance made the impedance high at some frequencies. Telephone-line impedance is nominally 600 ohms. That would explain why telephone headphones use to be at least 150 ohms. Earphones for lightweight aviation headsets are nominally 600 ohms. But that doesn't say a thing about why GE picked a nonstandard speaker impedance for installation in their entirely electronic cordless phone. All the other cordless phones I've had worked fine with a 32-ohm headset, even one 8-ohm headset. Hmmmm... how long have headset-ready cordless phones been available? Did any of your phones operate at 2.4 GHz or have DSS? Plantronics says they don't recommend their 32-ohm headsets for any of these phones. It sounds as if a lot of manufacturers are using higher impedances. There must be inexpensive 150-ohm headsets or earphone elements available. If only specs were easier to find! Simpler is to get another phone. I'm so spoiled by the headset that I can't hold an earpiece any more. According to Plantronics, buying another phone may not solve the problem. I bought a V-tech branded Radio Shack because it showed up $100 off and was nice and small. Dropped it once too often, replaced it with another RS unit made by Uniden that's both inexpensive and really nice, still on sale at RS. My cordless phone/answering machine cost $30. GE has a headset for $35, but I'd rather do without than buy theirs, under the circumstances. When they said "headset ready," didn't they imply that a standard mobile headset would work? I'll watch for a suitable headset or microspeaker. -- Best Regards, Lloyd |
#4
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Headsets for cordless phones
Did your GE phone list which headsets would work with it? If not, you
might try posting your question on a newsgroup slanted toward cordless phones or electronics, asking if anyone has the model phone you have and is using a headset. You might get some good replies. Good luck. |
#6
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Headsets for cordless phones
In article ,
"Clifton T. Sharp Jr." wrote: Lloyd Randall wrote: "Clifton T. Sharp Jr." wrote: All the other cordless phones I've had worked fine with a 32-ohm headset, even one 8-ohm headset. Hmmmm... how long have headset-ready cordless phones been available? Did any of your phones operate at 2.4 GHz or have DSS? Plantronics says they don't recommend their 32-ohm headsets for any of these phones. It sounds as if a lot of manufacturers are using higher impedances. The V-tech and the current RS/Uniden were both 2.4GHz and DSS. Plantronics' headset gives *me* good volume with them, but their boom mike gives low outgoing volume on those two and two other phones I tried it on. (Works fine with the cell phone, though.) I currently use a $30 RS binaural headset with the RS/Uniden phones and like it. Oh no! I have to worry about the mike, too? Plantronics gave the M110 a three-position switch so the user could choose -45, -50, or -55 db. You can't please everyone. One caller preferred -45 and another -55, so I leave the switch at -50. Any equipment you plug into the line input of a stereo amplifier should work because it's all supposed to have a signal of 1 volt and an impedance of 600 ohms. Phonograph signals also have electrical specifications, allowing one to use different turntables or cartridges. Telephone equipment used to adhere to electrical specifications. Aren't there electrical standards for the signals at the headset jack of a phone? What a mess! You've gotten me curious about Uniden/RS. -- Best Regards, Lloyd |
#7
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Headsets for cordless phones
In article ,
Andrew White wrote: You're getting very technical, but I doubt you found the right reason. The headset might just be junky. I tried a whole bunch of different ones until I found a perfect one that sounded great: Panasonic KX-TCA88. They are cheap too, under $25. I don't think my Plantronics is junky, but it could be that Panasonic has done a better job designing a headset to work with a phone like mine. The KX-TCA88 doesn't seem to be available any longer, and I don't know if newer models are as cheap. Panasonic headsets have pleased owners of some 2.4 GHz phones. I wish I knew if that means they would excel on all 2.4 GHz phones. -- Best Regards, Lloyd |
#8
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Headsets for cordless phones
I've been trying to find a headset to work with my Uniden phone. I've
tried 4 headsets. On 3 of them the caller can barely hear me. All of them had the mic positioned some distance from my mouth. The one that worked had the mic positioned very close to my mouth, but it was over the head design and I can't stand wearing it. The first two I tried worked great on my friend's cell phone and were designed for his headphone. The third was designed for cordless phones according to the package. I just don't get it. |
#9
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Headsets for cordless phones
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