Special Interfaces

Sometimes the most useful accessories are those that simply provide connections to other accessories. This is growing increasingly important as the size of notebook computers continues to decrease. The diminutive form factors of new ultralight notebooks and Tablet PCs limit the number and variety of connectors that can adorn their rear and side panels. To be able to connect with some peripherals, these systems have to be equipped with special interfaces that attach to USB ports and can be slipped inside PC Card slots.

USB

All recent notebooks are equipped with a USB port ”in fact, in many cases there are two of them. A handful of notebooks have even more. With a speed of 12Mbps, these connectors are orders of magnitude faster than the serial ports they replace. They come in very handy for connecting keyboards, pointing devices, external data-storage devices, printers, and many other peripherals.

In those increasingly common cases where just one or two USB ports are not enough, some companies have begun offering notebook accessories designed to enhance a notebook's USB connectivity. This is in the form of a PC Card with a dongle or short adapter cable that can connect to one or two USB ports. Before you buy one of these cards, note that the original USB standard is being slowly but surely replaced by a much faster standard: USB 2.0.

USB 2.0 Cards

For older notebooks with slower USB ports, CardBus PC Cards are available for providing the high-speed connectivity available with USB 2.0. The maximum speed for this standard is 480Mbps. This is ideal for connecting external storage devices such as hard drives, CD/DVD drives, and tape drives . Note also that these cards will still be compatible with older and slower USB peripherals such as keyboards and mice.

Portable USB Hubs

USB devices are now so plentiful that often a notebook needs several USB connectors. Providing these connectors is relatively easy, however, because the USB standard enables one system to connect to up to 127 peripherals. All you need to do is connect a USB hub to one of your laptop's USB ports to gain an additional set of connectors. By daisy-chaining hubs together, you can continue to attach devices up to the theoretical maximum specified in the standard.

Most USB hubs are too large to consider for mobile work, but some manufacturers are selling miniature USB hubs that are fairly small and lightweight. By attaching a four-port USB hub, you will quickly and effectively add three more USB connectors to your laptop.

FireWire Cards

If you are doing video work on your notebook, an IEEE 1394 or FireWire connector is mandatory. Only Sony and Apple currently equip their notebooks with this high-speed connector, however. For those notebooks that lack it, a small number of CardBus PC Cards that provide a 1394 port are available.

Note that there are two versions of IEEE 1394 devices available. The original IEEE 1394 version (or 1394a) has a maximum speed of 400Mbps. The new 1394/800 or 1394b version has a maximum data rate of 800Mbps.

Also note that there are two connectors used by IEEE 1394 devices. The tiny 4-pin connector is used by Sony laptops and by most digital video camcorders. (Note that Sony refers to IEEE 1394 by its trademarked name i.LINK.) Apple, which refers to IEEE 1394 by its trademarked name FireWire, uses a larger 6-pin connector. The extra two pins on this connector can be used for supplying power to peripherals.

Serial Ports

The venerable RS-232C serial port has been replaced to a large extent by the much faster USB connector. Nevertheless, there are still some environments and legacy equipment that require this connector. For those notebooks than need more than one serial connector ”or for those recent notebooks that lack one altogether ”there are PC Cards and USB devices that provide multiple serial connections.

Parallel Ports

As with the serial port, the USB connector is quickly replacing the Centronics-style parallel printer port. Because of its decreasing usage ”and its large size ”some notebooks are omitting this connector to save space for other components . If you still need a parallel port, this capability can be provided by a PC Card adapter or a USB/parallel adapter.

SCSI Adapters

For many years , the fastest connector on personal computers was the SCSI port. Nowadays, this connector is being supplanted by both the USB 2.0 and the IEEE 1394 connectors. No current notebooks ”and very few older ones ”have a SCSI connector, but as with serial and parallel ports, this capability can easily be provided with a PC Card adapter. If you need to use SCSI devices, you can attach a CardBus-based SCSI adapter, such as the Adaptec SlimSCSI 1480, or use a USB-to-SCSI converter, such as the Adaptec USB2Xchange.

Signal and Control I/O

Some special applications involve device control and signal monitoring. In these cases, the computer must monitor the signal outputs from various sensors and then send out control signals to activate various types of equipment. A laptop can easily take on this application when equipped with a PC Card that can accommodate several different analog/digital and digital/analog converters.

Keithley Instruments (www.keithley.com) sells a number of these cards. A typical example is its Model KPCMCIA-12AI-C PC Card. This card has 16 analog/digital converters that can measure analog input with a precision of 12 bits. It also has four digital channels that can accept and send out digital signals.

Miscellaneous Devices

For those times when you have to operate a notebook in a completely dark environment, Targus sells a small light. The light gets its power from the notebook's USB port.