Personal Digital Assistants

© Mercury Communications Ltd - November 1993

2007 network writings:
My TechnologyInside blog

The personal digital assistant (PDA) is a new computer product that has been hyped and eulogised more than any other product introduction for many a year. What is interesting about PDAs and what has caught the media's interest is that the PDA, a term coined by John Sculley, then Chairman of Apple, in January 1992, is that the concept represents a clean break from the past that consists of " a sophisticated set of software and hardware technologies that will result in whole new classes of intelligent products". At the launch of the MessagePad Sculley was ebullient by billing it as the launch of "defining technology of the digital age" and claiming it was at the centre of the convergence of computer, communications, and consumer electronics.

Fig 1 - US Installed base of PCs & PDAs Split by User Interface Type ( BIS Strategic Decisions)

The PDA, along with Microsoft's NT all-singing-all-dancing operating system (TW #13), has gained world leading notoriety as well. Firstly, the actual launch of the product was at least twelve months behind what was originally forecast by Apple, this allowed a small UK company called Amstrad to steal Apple's thunder by introducing their 'PDA' earlier than Apple (although Amstrad's product is not really a PDA). Secondly, although the potential of PDA concept is tantalising, the actually of what has been delivered in the first product (Figure 2) leaves a bit to be desired. To quote Byte, "prices are high, handwriting recognition is marginal, and communications are incomplete". Certainly, the supporters of the PDA concept are forecasting a very healthy share of an already large market by the end of the decade (Figure 1).

However, rising above this rhetoric it is quite clear that PDAs mark a watershed in the PC industry and hold a phenomenal amount of potential to deliver the integration of computing and communications we all want to see. However, we should remember that the implementation of communications facilities and services on PDAs are just as applicable for the conventional portable notebook that we all know and love. In this issue of Technology Watch I will explain what makes PDAs tick and what are the potential services that could be delivered into the palms of our customer's hands.

So What is a PDA?

There is no strict definition or industry consensus of what a PDA is, the nearest to this consists of a mixture concepts, features, technologies and vision of the future of mobile computing. All these originate with Apple and are now several years old. Many cynics have said that the PDA derives from the acceptance that Apple are no longer a force in the corporate PC market having conceded this to Microsoft Windows and the hundreds of PC clone manufacturers. Therefore attacking the largely untapped consumer market with the PDA concept would provide Apple with an almost unlimited growth potential in coming years. An early mistake of Apple that led to this situation was that the Apple Macintosh was not an open machine throughout most of the 1980s. They did little to encourage 3rd party software developers to write applications for Apple machines. Therefore the energy of most these companies went into the open PC architecture. Only in recent years have Apple changed their views in this matter and also faced up to the very high cost of Apple machines compared to PCs by slashing RRPs in the early 1990s. They have learn their lesson well and are not about to repeat history with the PDA. Apple intend to make their 'NEWTON INTELLIGENCE' operating system (OS) the standard for PDAs by extensively licensing it to other manufacturers. So what is a PDA? This best described by going back to early Apple Newton literature and replaying what they were saying a couple of years ago about "the new foundation for intelligent computing" and let you contrast them with the standard notebook.

Products that actively help you

Newton products will work more like assistants than just tools.

Products that let you record ideas and information the way you're used to.

To begin using a Newton product, you simply pick up the Newton pen and start writing on the screen.

Products that let you organise information flexibly

Newton products organise and store the things you write down in a form that lets you use and reuse individual pieces of information in a variety of ways.

Products that let you communicate easily - anytime, anywhere.

On their own, Newton products are great assistants, but they're also great communicators. They connect easily - through both wireless and wired connections - with one another and with printers, faxes, pagers, computers, and other devices.

PDAs are not substitutes for PCs; they are different devices for different markets. PDA designers think their devices are for consumers of information rather than creators of information. Therefore, input will be brief and sporadic and mainly limited to selection from menus. Those that need to enter lots of data are better off with a conventional notebook computer.

In 1992 Apple were also promoting a wide variety of visionary products based on the Newton (Figure 3). It is fair to say that they are now back-peddling in this domain.

It is this issue that has caused the disappointment with the launching of the Newton PDA. As put by Byte, the MessagePad's school report shows A- for effort, F for affordability, D for applications, handwriting recognition C+, and communications - incomplete!

There are several portable computers that have been announced in recent months that have claim to be in category of the PDA. But the only true PDAs are the Apple MessagePad - the very first example of Newton technology and the Tandy/Casio Zoomer. Although superficially similar, the underlying architectures are radically different.

MessagePad from the Champion of PDA Technology, Apple

The MessagePad, as the first example of a new world genre, undoubtedly displays Apple's radical departure from the way things are (or were). It is a pen input device based on a reduced instruction set computer (RISC ) equipped with a multitasking operating system call 'Newton Intelligence'. It is packaged is a small case of about 7˝" by 3˝". A lid folds back to show the 6" by 3" liquid crystal display (LCD).

It is good news for the UK that the Newton is based on a British designed and manufactured RISC chip; the Arm, which originated in Acorn Computers in Cambridge. In 1990 it was decided that to maximise the potential for the device a separate company should be formed financed jointly by Acorn and Apple. Arm today is a major contributor to the profits of Acorn. the 20MHz Arm610 chip is positioned 1/3 down from the top of the printed circuit board shown in figure 4 above.

For storage, the Message Pad uses a single PCMCIA 2.0 card. It is actually a superset of the PCMCIA called TRIMbus that is actually a full 32-bit device that can support memory, disks, and communications devices, as we shall see later. It is equipped with 4Mbytes of read only memory (ROM) that contains the 'Newton Intelligence' and other application software. It also contains 640kbyte of random access memory (RAM) that contains users data.

Pen Digitiser

The MessagePad is based on using a 'pen' for inputting data to the computer. The primary advantage of the pen is not necessarily to write, but rather to point, to manipulate the user interface without the need for a keyboard, mouse, or somewhere to rest the arm. The pen enables mobility and opens up a panoply of applications where workers and managers need to gather data while on the move. Pen input works because of a digitser. The MessagePad uses two transparent, resistive underlays which generate interrupts to the computer when the pen tip temporarily forces the two conductive layers together as shown in figure 5. By measuring the resistance in x and y axis' the computer can calculate the physical position of the pen.

Text Interpreter

MessagePad supports textual input via the pen. It is fair to say that text recognition is still a bit of a hit-and-miss affair, it works exceptionally well or not at all! Like most text interpreters the MessagePad requires you to undergo a 'handwriting practice' session to allow the software to learn the characteristics of your personal writing style. It takes about 150 words to train the interpreter. MessagePad also uses a dictionary, so if it does not recognise a particular word you can enter this into the dictionary so that it will be correctly recognised the next time you use it.

From talking with many people who have experienced this particular hand writing interpreter, it would seem that from the beginning you can either use quickly or not at all. Certainly, if writing is up to the 'school marm' standard and the stokes use match the 'correct' style it is easy to use. However, if any of your characters deviate from this norm great difficulties result. However, after a few weeks when you accept that you need to be prepared to adapt your writing style to that accepted by the MessagePadyour recognition hit-rate takes a leap upwards. There is also a 'recognition preferences' sections that allows you to fine-tune both the handwriting recogniser and the graphics interpreter for certain situations e.g. to recognise numbers and punctuation.

Although not fully available yet on the MessagePad Figure 6 shows an example of digital ink capability. Digital ink can include handwriting and control gestures and is saved in the form as entered into the computer. For example, Ink development's Notetaker, can be highlight and boldface hand-written text. The difficulty of implementing accurate handwriting recognition has caused several vendors to push digital ink as a replacement for text recognition.

Newton's Operating System

Several pen computers use operating systems derived from the desktop environment: GEOS, Pen for Windows from Microsoft, and GO's PenPoint for example . Apple Newton's 'Intelligence' was designed from the ground up to support PDAs. There is also an advanced PDA operating system from General Magic called magic Cap, but this is not yet available on commercial products.

Some parts of Intelligence derive from conventional Apple Mac software, including bits of Quickdraw and the ability to work with AppleTalk network standards. Written C and C++ intelligence is hardware independent and is capable of being ported to a processors other than the Arm chip. The user interface also uses a new language called NewtonScript which is the development language for all Newton applications. Intelligence is split into four major parts: (1) Recognition Architecture, (2) Communications architecture, (3) Information architecture, and (4) the Intelligent Assistant. The Recognition Architecture contains the handwriting recognition engine designed in Russia, by ParaGraph International, a US / Russia joint venture. While Newton's Communications Architecture supports a wide variety of I/O devices via MessagePad's internal RS-422 port. PCMCIA card slot, and its 19.2kbit/s infrared transceiver.

What sets Intelligence apart from desktop operating systems like UNIX and DOS is its Information Architecture. Rather than being based on the 'old' file oriented model we all know, it is based on objects or data. It is one of the first object oriented operating systems to hit the market. There is much talk of Microsoft's Cairo project and Taligent's (a joint venture between Apple, IBM, and Motorola) Pink that will soon be here, but Newton beat them to it. All these three components interface with the Intelligent Assistant that makes the connection between the user's actions and the data. For example, if you ask MessagePad to 'fax to Lisa', the Intelligent assistant automatically assumes that the sketch you draw on the screen is the object you want to send. Next, it locates the Lisa in the object database, if there is more than one it presents the list on the display and asks you to select which one you want to send the fax to.

Sharp's PT 9000

The Sharp PT9000 is a good example of a non-Newton PDA. It has all the characteristics of a PDA but is radically different inside.

Rather than designing everything from scratch from the ground up as Apple did with the Newton, Sharp has used off-the-shelf components for the whole system. and uses GEOS from Geoworks for its operating system. Bundled with GEOS is GeoWorks, a word processor, spreadsheet, communications software, and a database manger.

Tandy Z-PDA or Zoomer

Deriving from a partnership between Casio and Tandy, the Zoomer, whose name derives from a corruption of the back end of the word consumer' provides very similar functionality to the MessagePad. In architecture it is very similar to the Sharp PT9000 (Figure 8) in that it uses GEOS and therefore has similar functionality to that found in the Sharp PT9000. The Zoomer , like Sharp, uses a low power version of the Intel 8086. Additional applications include a dictionary, spell checker, thesaurus, and a translator for 26 languages (!), and a world time clock. The Zoomer measures 4" x 7" x 1" and weighs less than 1lb.

Unlike the MessagePad the handwriting recognition engine, called PalmPrint (developed by Palm Computing), does not need to be trained.

The Zoomer also contains the mandatory PCMCIA slot an RS-232 serial interace, and an infrared transceiver that can you can use to exchange data at 9,600 bit/s.

The AT&T EO Communicator

The EO 440/880 (Figure 9) are not really PDAs in that it is both too expensive and large to fit into that category. It weighs in at 1.8kg and EO880 model is sized at 12" x 9" x 1" and has more commonality with classical pen based computed such as manufactured by Grid. However, it does integrate wireless communications effectively. In the US a free subscription to AT&T's EasyLink® service is thrown in. EasyLink consists of AT&T Mail, AT&T FAXsolutios, and Electronic Data Interchange (EDI), Telex, and Information Services.

AT&T Mail can be considered to be a communications manager. You can set up lists of people or sites that should receive communications and the type of output that they require, e-mail, fax, telex, post, or whatever else they need. Then, when you send a message, data, or a document, your list is automatically invoked and Mail manages the delivery to each individual according to your instructions i.e. you do not need to send the same message over and over (since this article was written AT&T have discontinued the EO and closed the company down.

PDA Communication Services

One of the core parts of the PDA vision that still has not been met is the Sculley 'Products that let you communicate easily' vision. Although there are many reasons for this situation, In Europe at least, the problem really lies in the domain of public operator or network provider being not sufficiently cognisant of the potential or not joining in with the vision of the ubiquity (or need) of mobile computing in coming years. However, this should be seen as an opportunity rather than a problem!

We should remember that is key vision for all PCs including palmtops and notebooks. There is nothing special about PDAs at this time that would dictate communication products and services that would be different from other portable machines. Yes, applications would need to have a pen input capability and need to work under a different graphical user interface (GUI) to that found on a desktop (Newton Intelligence, PenPoint, GEOS, Pen for Windows etc.) but that is all. The underlying services and physical communication interface port are just the same, RS-232 serial port, infrared port, and a PCMCIA slot.

Let us look at what communication 'services' are possible on a PDA or notebook computer now or over the two to three years. This means that we will ignore video services for the moment which sits more comfortably in the desktop domain with the current state of technology.

Serial port

The serial port on a PDA is the same as on a desktop machine and thus it is possible to connect to printers or to modems in the traditional way. Having to 'plug in' limits the usefulness of this port when out and about.

Infrared port

The infrared port on PDAs and notebooks is an optical link that enabled the transfer of data in 'docking situation' to and from the a desktop machine. Quite high data rates are possible but, as yet, no generally accepted standards exist making all links proprietary in nature. This limits the usefulness of the port to a great extent. The capability is similar to that achievable over an RS-232 line with the added advantages of cordlessness. The problem in the past has been that infrared links have been fussy in that their beam width has been too small leading to lost data.

However, a recently formed consortium of manufacturers have recognised this as a major stumbling block in the vision. The group call themselves the Infra red Data Association (IRDA) and comprise of 75 companies including Hewlett Packard, AT&T, Intel, Microsoft, Olivetti, Toshiba, and Hitachi. The group intends to define standards that will allow inter working between different computers. For example it could soon be possible to:

Send or receive a fax at a suitably equipped public telephone box - without the need to plug in.

Print documents remotely from your laptop without the bother of plugging in

Collect full bank statements from ATMs (with encryption of course)

Standards already exist for infrared communication in the area of remote control for TVs and HI-FI.


The third Input/output socket is the PCMCIA slot. A PCMCIA card is about the same size as a standard credit card but is thicker and has a connector on one end. It is the standard peripheral connector for notebook computers. It is possible to buy many peripherals in the PCMCIA format e.g. modems, fax interfaces, RAM, and hard disks. The first two examples obviate the need for external box when connecting to a standard analogue telephone line.


It is also to use the PCMCIA card to interface the PDA or notebook to an office LAN. The MessagePad has an AppleTalk LAN interface already built in. There are several PCMCIA cards on the market now that will allow connection to a standard Ethernet LAN. Indeed Novel in their LAN management software, is introducing full support for mobile notebooks using a LAN. This means that the system is cognisant of a particular machine being a notebook and automatically manages the transfer of files (messages) to and from the machine when docked to the LAN. It also manages the automatic backing up of data when docked.

Radio Ports

The most Avante garde use of the PCMCIA slot is the possibilities of communications without physical connection over a long distance (unlike infra red) using radio. This concept lies at the very heart of the PDA vision outlined by Sculley.

Using radio it is possible to support all the applications as epitomised by AT&T's EasyLink described earlier. The radio port is called a radio modem. Several radio standards are applicable for use in this application:

2.4GHz Unlicensed Band.

In the UK the Radiocommunications Agency has given spectrum in the 2.4GHz ISM (industrial, scientific, and medical band) for unlicensed low-power spread-spectrum (see TW #1) applications. This band can be used for point-to-point communications or broadcast based radio-LAN applications. Figure 10 shows UK's Symbionics design for a Type 2 PCMCIA card using frequency hopping spread spectrum techniques. The technology is based on the new IEEE 802.11 standard for radio LANs. Figure 11 below GEC Plessey Semiconductors ISM PCMCIA card.

DECT Cordless Standard.

The DECT cordless standard is being used for radio LAN applications e.g. Olivetti's Net3 system. DECT is potentially an ideal standard but only for use in an office environment inside a building . What makes DECT interesting for LAN applications is that it can support high data rates by concatenating time slots. DECT can support simultaneous 32kbit/s ADPCM voice and 1Mbit/s data transmission. This has been recently demonstrated by Apple on their Powerbook laptop PC.

GSM & DCS 1800

Both ISM band and DECT based interfaces can only be used on a local basis. Ideally, what is required to provide full coverage throughout the UK. It is here that the digital mobile standard, GSM, and the PCN standard, DCS 1800 steps in. A full integration of the PDA vision with a digital mobile telephone would provide the coverage users want. However, unlike DECT, GSM and DCS 1800 only supports fairly data rates of up to 9.6kbit/s. The standards needed for reliable transmission of data over a GSM channel are yet to be defined and a number of problems still need to be ironed out. This will not take place until 1994. Analogue networks recommend that data is transmitted at only 1.2 or 2.4kbit/s.

An interesting standard called Cellular Digital Packet Data (CPDP). CPDP cellular data networks will share spectrum with voice networks by interspersing 19.2kbit/s data packetswith voice during periods when channels are unoccupied by a voice call. No new voice call may pass over a cellular link until 5 to 10 seconds after the previous call has been disconnected. CPDP uses this 'guard band' to move data.

Paging and Messaging

Paging networks are based on radio cellular systems. They use low power VHF channels (140MHz) and in general provide only one-way broadcast facilities. Bearing in mind the 'simplicity' of integrating paging capability into a PDA it is not surprising that Apple has signed up many paging organisations to provide paging functions of the MessagePad. This includes Mercury Paging in the UK. Motorola has already designed a PCMCIA pager unit called NewsCard.

The potential for paging services is huge. Future developments will include smoother connections to e-mail. Most pager services involve dictating your message over the telephone to an operator who enters it into paging system. Most, LAN users want to be able to use cc:Mail or Microsoft Mail. The is also much opportunity for broadcast information services such as stock market share values or news bulletins.

Dedicated Radio Data Networks

There are four two-way data-only radio networks in existence in the UK: Cognito, Paknet, Hutchison Telecom, and RAM Mobile Data. The first two operate at VHF frequencies while latter operate at UHF. Ram operates in the UK as well. These are able to support low cost, low data rate, packet data delivery to mobile computers using dedicated mobile modems plugging into a PCMCIA slot on a notebook computer. Such systems are principally used to provide store and forward e-mail services for those on the move. Hutichison uses the Motorola radio data link access protocol (RD-LAP) which is said to provide up 9.6kbit/s capability. RAM currently transmits at a lower data rate of 8kbit/s which includes error correction and security overhead.

The Risk of Ignoring PDAs

Apple's MessagePad has received considerable criticism in the press since its launch in August. This is mainly because of the disparity between Apple's articulated vision and the reality of the first delivered product. However, I believe this should not be taken too seriously. The PDA is only at very embryonic stage of development and will undoubtedly be a major computing force in coming years. Apple has sold 50,000 MessagePads in a little less that two months. Although early sales have been to 'gadget freaks', this has been far higher than Apple ever expected. It is forecasted that Apple will ship 200,000 units in its first year. In comparison, HP have only sold 300,000 of its 95LXs in the three years it has been on the market.

Although MessagePad is not yet ready for the consumer masses it real near term role is as a platform for corporate applications such as piloting mobile client / server products. For the more technical minded Newton technology provides a working model for object oriented programming. Newton (and PenPoint) delivers today what Cairo and Taligent promise for the future.

Products like Apple's Newton will help companies service mobile executives. The communications possibilities presented by the combination of pagers, e-mail, fax, and forms based applications will stimulate a whole new class of systems in large companies. Large companies and telecommunications operators are at risk if they are tempted to ignore devices like the Newton, EO Personal Communicator, and the Tandy/Casio Zoomer. These are not toys and do not deserve to be treated as such but we should not also over react and put PDAs at the centre of the universe.

Whatever else, mobile data transmission is going to be a huge market by the end of the decade, Ovum fpredict that there will 915 thousand users of mobile data services in the UK with 9.2 million worlwide. Perhaps Sculley's original vision for PDAs is valid after all?

Mercury and Cable & Wireless acknowledge the trademarks of all the companies referred to in this article.

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