Our new answer: It doesn't matter.
Digital systems include analog components. Analog systems include digital components.
There is no difference in voice quality or system durability.
Make your decision based on features and price, not internal technology.
Part of the "magic" of Panasonic's digital super-hybrid phone systems is that they are backwards-compatible.
Just as a new Nikon camera can work with Nikon lenses made decades ago, a brand-new Panasonic KX-TD system, can work with Panasonic KX-T analog multi-line phones, even those made long ago.
Our own office system has some of the newest digital phones, plus FOUR generations of analog multi-line phones, plus some analog single-line phones -- and they all get along, and work fine.
When connected to a new digital system, older phones will be able to perform many new tricks, for example:
Chances are, you'll want some new digital phones to take advantage of some of their unique features -- such as the call log and Rolodex-style dialing index on the KX-T7456 -- but you can make an orderly and gradual transition, as your needs and budget dictate.
Sure.
First, some background...
Each phone jack in a Panasonic digital system has the usual green, red, black and yellow wires.
The black and yellow wires are considered the DATA PAIR, and carry power plus digitized voice and information that a digital phone needs for full functioning on all the lines connected to your phone system. A digital phone will work just fine with just two wires (one pair).
The green and red wires are considered the VOICE PAIR, and this pair is all that is needed for an ordinary single-line phone, or a modem, fax machine, credit-card terminal, answerer, etc. A single-line device can have access to all your lines, intercom, and most features.
When a digital phone is plugged into a 4-wire jack, the analog circuit from the green and red wires is passed through the body of the phone to the XDP jack on the back of the phone.
If you don't have a digital phone plugged into a particular 4-wire jack, you can plug in an analog phone or gadget, and it will connect to the proper green and red wires, and ignore the black and yellow data pair.
If you don't need to use the XDP on a particular digital phone, that analog circuit can be connected to another jack, even in another room.
Two answers, and they're both "yes."
(A) If you're talking about a Panasonic multi-line phone designed to be used with a KX-T hybrid phone system, (phone models such as the KX-T61630 or KX-T7730) you can plug it right in and it will work fine, and even do some new tricks that it could not do with an analog system. Be aware, however, that the analog phone requires all four wires in a jack (the data AND voice pairs), and will not work if you have enabled the XDP function for a particular jack (program step #600).
(B) If you're talking about a self-contained two- or three-line phone, such as a Panasonic KX-T3175 (a phone that is NOT designed to work as part of a phone system with a central control unit), you have two choices:
Two cautions:
Both of these discontinued digital spread-spectrum cordless phones use the same handset.
The 7890 is a three-piece system. The handset goes on a small cradle for charging, and the cradle just needs AC power -- it does not need a phone jack. The third part of the system is a base with two antennas, that connects to a phone jack and an electric outlet. The handset never has to go near it, and it can be mounted in a phone closet, or up high in a building for maximum range.
The KX-TCS970 was discontinued in the Spring of 1998. It was a more conventional two-piece system. The handset had to be returned to its base for charging, and the base had a speakerphone and touch-tone dialing pad.
The 7890 was discontinued a few years later. It came with two rechargeable battery packs, the 970 came with one.
This feature can be very useful if you want to program a single-line phone to call 911 or another important number, and it can also make a modem or fax choose a specific line, or even any available line, before dialing out. Look in the large User Manual, in the section called SLT Features, for "Pickup Dialing (Hot Line)".
Programming this is a two step process. First you program the phone number that you want to dial, or a code such as 9 or 83), and then you activate the feature.
If you want to program a jack that will be used by a modem, temporarily put a single-line phone into the jack, for programming.
The best way to make a call with a Panasonic proprietary multi-line phone, is to simply tap an unused "CO" line button, and immediately start dialing the number. You don't even have to wait for dialtone. In a digital system, you can tap a button programmed for automatic dialing, and it will choose a line, turn on the speaker and microphone, and dial the call. In an analog system, you first tap a line button or the SP-PHONE button, and then tap the programmed button.
The default programming in Panasonic systems is to connect you to the intercom when you pick up the handset. This setup encourages you to dial with the speakerphone instead of the handset -- a very sensible timesaver, since there is a good chance that your call won't be answered or you'll be put on hold for awhile before you get to talk.
However, there are some people who insist on making calls the old-fashioned way, and the thoughtful folks at Panasonic have provided a way for you to grab an outside line when you pick-up the handset. The procedure is called Auto CO Hunting in analog systems and Preferred Line Assignment - Outgoing in digital systems. The instructions are in the User Manuals.
(8) How can I use a single-line phone to retrieve a call that was put on hold at another phone?
With a digital system: You can get a call that was put on hold elsewhere,
by dialing 51 plus the intercom number where the call was put on hold. You can also dial
53 plus the line number, with two digits (e.g.: dial 5302 for line #2).
With an analog 308 or 616 system: You can get a call that was put on hold elsewhere, by dialing 5 plus the intercom number where the call was put on hold.
With the analog 616 system: You can also dial 58 plus the line number, with one digit (e.g.: dial 582 for line #2).
With the analog 1232 system: You can get a call that was put on hold elsewhere, by dialing 5 plus the intercom number (three digits) where the call was put on hold. You can also dial 53 plus the line number, with two digits (e.g.: dial 5302 for line #2).
(9) How can I use a single-line phone to join in a conversation?
Someone with a multi-line phone has to set up a conference call and include the single-line phone.
(10) How do I use Call Waiting in a digital system?
If you are using a display phone, you should see "EFA" in the display just above the center/bottom button. EFA stands for External Feature Access, and you can use this button to alternate between calls when you get a Call Waiting signal from the phone company.
If you are using a non-display phone, you should program your FLASH button to activate Call Waiting. Look in the Installation Manual for program number 990, field 3.
If you are using a single-line phone, press FLASH (or hang-up briefly) then dial 6.
(11) How can I make my phone automatically dial the 9 for Centrex calling?
Programming this is a two step process. First you program the phone to dial 99, (or 9 PAUSE 9, if 99 doesn't work), and then you activate the feature. Look in the large User Manual, for "Pickup Dialing (Hot Line)".
When you press the SP-PHONE button or pick up the handset, the phone will dial 9 to get the first available line, and then dial 9 to break Centrex dialtone and give you a dialtone you can use to make a normal call.
If you want to make an intercom call, you can press the INTERCOM button after the phone has selected an outside ("CO") line.
(12) Which Panasonic phone system can provide roll-over from a busy line to another line?
None. This feature, also known as hunting, Incoming Service Group (ISG) and rotary, and Call Forward on Busy, can ONLY be provided by your phone company.