Unfortunately, this phone is no longer available. If you have one, you're very lucky.
Panasonic's longest-range cordless phone.
	Bigga Range than GigaRange!
Since early 1998, phone makers and dealers have been screaming about 2.4GHz cordless phones, with high security, great voice quality, and long range. The first two claims are usually true, but the long-range claim is usually baloney.

(1) It's a basic fact of physics, that with all else being equal, radio transmissions reach farther at lower frequencies. 

(2) It's a basic fact of life that the 900MHz Panasonic KX-TD7890 has longer range than any 2.4GHz cordless we know of.

(3) The Panasonic KX-TD7890 comes from the Business Communications Division of Panasonic, and their consumer phone division and most Panasonic phone retailers prefer that you don't know about it.

The KX-TD7890 is a super-small and super-good single-line 900MHz cordless that works fine with Panasonic's KX-T phone systems, and by itself. You can plug the base into any ordinary phone jack.

The "D" in the model number indicates DIGITAL. This is a  DIGITAL SPREAD SPECTRUM phone that provides extreme security and long range; so all of you paranoids and long-distance dog-walkers will be very happy. It's great in large homes, office buildings, factories and apartment houses, and on farms, ranches and college campuses. We've sold lots of them to the Federal Government, including super secret warfare labs, Air Force bases and the Border Patrol.

Panasonic claims range of up to FOUR THOUSAND FEET between base and handset. AbleComm customers have frequently reported range of a half mile or more. One of our customers put the base up high in an airport hanger, and says he gets one-mile range!

I did a test when I got my 7890 a few years ago. My longest tape measure is not very long, so I couldn't actually measure maximum range; but here's the result of my first quickie test:

I put the base on my dining room table on the ground floor of my house. We live downhill from the street in front of our house, so the top of the antenna was probably 10 feet "below street level."

I didn’t have time for a hike, but I was able to DRIVE about four blocks, with the handset in my steel-bodied phone-filled Dodge Caravan, and voice quality was ABSOLUTELY PERFECT.

Absolutely no background hummmmmmm. Absolutely no background hissssssssss. Absolutely no over-emphasized sssssssibilants. And no distortion. And no too-high sidetone. And it's not as heavy as a brick. Or as big as a book. And the volume is not low, in either direction. And no one could listen-in on my conversations.

Panasonic KX-TD7890 has no Caller ID and no headset jack and there's no touchtone pad in the base. It does have great sound, super security, small size and long range. There's no two-line version, and none with a built-in answerer. Most telephone retailers don't know it exists, but AbleComm sells tons of them!

In short, the Panasonic KX-TD7890 had none of the shortcomings I suffered with on every digital phone I tried before this one. It was the first one I was not embarrassed to use, or to sell.

I was really been DOWN on digital phones until I tried the 7890. I called them "not ready for prime time," and seriously doubted that there’d ever be a successful digital spread spectrum phone for general consumer use.

Spread spectrum technology, also known as "frequency-hopping," was co-invented by actress Hedy Lamarr during World War II, to help direct American torpedoes at Nazi battleships, without them getting jammed and sent off-course.

WW2 electronics were pretty primitive, and Hedy’s system used a mechanical switching system, like a piano roll, to shift frequencies faster than the Nazis could follow them. 

More recently, spread spectrum was combined with digital technology, for spy-proof and noise-resistant battlefield communications. It was secure, but strictly low-fi.

If some GI in the jungle complained to the general that his walkie-talkie sounded lousy, the general could reply, "too bad, you’re a corporal, shut up."

That privilege of rank, however, does not work in the consumer electronics marketplace; and many people who bought and tried high-priced high-tech digital cordless phones, hated them and returned them. Some phone dealers, including AbleComm, refused to sell them…until we tried the 7890.

When connected to a Panasonic KX-T phone system, you'll have access to intercom, lines and features; but you'll have to do a bit more button-pushing than with the 7880 or 7885 cordlesses, and there are no lights to show multi-line status. You can use several 7890s in the same system, but don't put more than four base units in close proximity to each other.

The 7890 is a three-piece system. The base, which connects to the phone line and AC power, can go in your basement or phone closet, or up high in the building for maximum range. The little charging cradle needs AC power, but no phone connection, so you have tremendous flexibility in setting up and using the phone. You can keep the handset anywhere you have electricity -- even in a different building from the base. The 7890’s base has full intercom capability, with speaker, mic, electronic volume control and page button. If you have a garage or a barn or a guest cottage or a pool cabana with electrical power but no phone wiring, you can keep the handset there and the base in your house, and have both phone service and intercom in the second building.

The charging cradle is wall-mountable if you want to keep it handy but out of the way. The phone sits upright in the cradle, and looks great on a desk, with a tiny footprint, roughly 2.75 x 4" -- about as big as a coffee mug. The handset can face forward or backward in the cradle, and also has a convenient slot where you can slide in a second battery pack (included) for charging and storage. There are charge indicators for both battery packs.  Panasonic claims talk time of about 3 hours, and standby time about 10 days.

The Panasonic price list says the 7890 should not be used "in the same facility" as any analog cordless. The instruction manual says the 7890 can be used with other cordlesses, but not 900meggers. My 7880 base is in my basement, one floor below the 7890 base in my dining room. When I put my 7880 handset near my 7890 handset or 7890 base, and turned the 7890 on, it did make the 7880 buzz badly. If I kept the 7880 handset about 15 feet from either part of the 7890, there was a little bit of not-too-bad background hum. 

The handset is a flip-phone design, also used on the discontinued KX-TSC970, with the look and feel of a high-quality cellphone. After about three years of use, the flip-open spring on my phone seems as strong as when it was new. 

The handset has a HOLD button, access to ten easy-to-program 20-digit speed-dial numbers, handset-to-base intercom, and it constantly scans among 32 channels to find the clearest one at any given time. It’s extremely comfortable to hold. It fits fine in a pocket, but there’s no belt clip. (We sell a nice holster that holds it.) The touch-tone buttons light up for dialing-in-the-dark, and flash rapidly when a call comes in. You can choose from two volume settings for the receiver, and two volume settings for the ringer, and even four ringing sounds. Cute.

The flip handset arrangement increases transmitted sound quality by reducing background noise and directing the voice to the microphone. The phone can be used with the flipper open or closed; microphone sensitivity is automatically adjusted for either position. Normal conversations sounded fine either way, but if you want to make a LOUD announcement in the intercom mode to attract the attention of someone near the base, keep the flipper closed and put your mouth on the mic.

The main base that connects to the phone line and an AC power source has a "Power Antenna System" -- two antennas in a "diversity" array, often used for wireless microphones on stage and for mobile communications. This configuration helps eliminate dead spots or multipath fading problems, and looks cool.

The KX-TD7890 digital cordless was a big surprise. I expected to hate it, but I’m in love. Unfortunately, so is my wife. She keeps snatching the phone from my desk.

by Michael N. Marcus
(This is an updated version  of a review published in  Teleconnect magazine.)