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33-545: Apple Desktop Bus (ADB) is a proprietary bit-serial peripheral bus connecting low-speed devices to computers. It was introduced on the Apple II GS in 1986 as a way to support low-cost devices like keyboards and mice, enabling them to be connected together in a daisy chain without the need for hubs or other devices. Apple Desktop Bus was quickly introduced on later Macintosh models, on later models of NeXT computers, and saw some other third-party use as well. Like

66-452: A wireless router . Aircraft carry automated microwave transceivers called transponders which, when they are triggered by microwaves from an air traffic control radar , transmit a coded signal back to the radar to identify the aircraft. Satellite transponders in communication satellites receive digital telecommunication data from a satellite ground station , and retransmit it to another ground station. The transceiver first appeared in

99-409: A "receiver". On a mobile telephone or other radiotelephone , the entire unit is a transceiver for both audio and radio. A cordless telephone uses an audio and radio transceiver for the handset, and a radio transceiver for the base station . If a speakerphone is included in a wired telephone base or in a cordless base station, the base also becomes an audio transceiver. A modem is similar to

132-448: A USB-based trackpad. In keeping with Apple's general philosophy of industrial design, Apple Desktop Bus was intended to be as simple to use as possible, while still being inexpensive to implement. A suitable connector was found in the 4-pin mini-DIN , which is also used for (but incompatible with) S-Video . The connectors are small, widely available, and can only be inserted the "correct way". They do not lock into position, but even with

165-427: A device does respond, it does so by saying it is moving to a new randomly selected higher address. The computer then responds by sending another command to that new address, asking the device to move to yet another new address. Once this completes, that device is marked live, and the system continues polling it in the future. Once all of the devices are enumerated in this fashion, the bus is ready to be used. Although it

198-447: A friction fit, they are firm enough for light duties like ADB. ADB protocol requires only a single pin for data, labeled Apple Desktop Bus . The data signal is self-clocking by sending a 0 as low for 65 microseconds and high for 35 μs, while sending a 1 uses the opposite timing. It is a multi-drop open collector design with pull-ups to 5 V and uses collision detection to avoid device ID conflicts as well as clock stretching on

231-419: A new address, only the other will then respond. This process continues until no one responds to the request on the original address, meaning there are no more devices of that type to enumerate. Data rates on the bus are theoretically as high as 125 kbit/s. However, the actual speed is at best half that, due to there being only one pin being shared between the computer and devices, and in practice, throughput

264-412: A time without obscure splitter units. Few mice or trackballs have them. In spite of being electrically unsafe for hot-swapping on all but a few machines, ADB has all the basic capabilities needed for hot-swapping (like modern buses) implemented in its software and hardware. On practically all original Apple Desktop Bus systems, it is not safe to plug a device once the system is powered on. This can cause

297-714: A transceiver in that it sends and receives a signal, but a modem uses modulation and demodulation. It modulates the signal being transmitted and demodulates the signal being received. Transceivers are called Medium Attachment Units ( MAUs ) in IEEE 802.3 documents and were widely used in 10BASE2 and 10BASE5 Ethernet networks. Fiber-optic gigabit , 10 Gigabit Ethernet , 40 Gigabit Ethernet , and 100 Gigabit Ethernet utilize GBIC , SFP , SFP+ , QSFP , XFP , XAUI , CXP , and CFP transceiver systems. Because transceivers are capable of broadcasting information over airwaves, they are required to adhere to various regulations. In

330-425: Is based around the devices having the ability to decode a single number (the address ) and being able to hold several small bits of data (their registers ). All traffic on the bus is driven by the host computer, which sends out commands to read or write data: devices are not allowed to use the bus unless the computer first requests it. These requests take the form of single- byte strings. The upper four bits contain

363-406: Is commonly used by police and fire departments. Digital transmissions tend to be clearer and more detailed than their analog counterparts. Many modern wireless devices operate on digital transmissions. In a wired telephone , the handset contains the transmitter (for speaking) and receiver (for listening). Despite being able to transmit and receive data, the whole unit is colloquially referred to as

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396-452: Is controlled by the proprietor , often under patent or trade-secret protection . Historically, most early computer hardware was designed as proprietary until the 1980s, when IBM PC changed this paradigm. Earlier, in the 1970s, many vendors tried to challenge IBM's monopoly in the mainframe computer market by reverse engineering and producing hardware components electrically compatible with expensive equipment and (usually) able to run

429-474: Is even less, as the entire system was driven by how fast the computer polls the bus. The classic Mac OS is not particularly well suited to this task, and the bus often gets bogged down at about 10 kbit/s. Early Teleport modems running at 2400 bit/s have no problems using Apple Desktop Bus, but later models were forced to move to the more expensive RS-422 ports as speeds moved to 14.4 kbit/s and higher. While Mini-DIN connectors cannot be plugged in

462-610: The TelePort modem . The first Macintosh to move on from Apple Desktop Bus was the iMac in 1998, which uses USB in its place. The last Apple computer to have an Apple Desktop Bus port is the Power Macintosh G3 (Blue and White) in 1999. PowerPC-based PowerBooks and iBooks still used the Apple Desktop Bus protocol in the internal interface with the built-in keyboard and touchpad . Subsequent models use

495-408: The "wrong way", it is possible to have trouble finding the right way without looking inside the circular connector's shroud. Apple attempted to help by using U-shaped soft plastic grips around the connectors to key both plugs and sockets so the flat side has a specific relation to the shell keyway, but this feature was ignored by some third-party manufacturers. Additionally, there are four ways to orient

528-441: The 1920s. Before then, receivers and transmitters were manufactured separately and devices that wanted to receive and transmit data required both components. Almost all amateur radio equipment today uses transceivers, but there is an active market for pure radio receivers, which are mainly used by shortwave listening operators. Analog transceivers use frequency modulation to send and receive data. Although this technique limits

561-589: The ADB software to interpret the signal. In more modern designs, an auxiliary microcontroller is always kept running, so it is economical to use a power-up command over the standard USB channel. The decoding transceiver ASIC as well as associated patents were controlled by Apple; this required vendors to work with Apple. In the Macintosh SE, the Apple Desktop Bus is implemented in an Apple-branded Microchip PIC16CR54 microcontroller. The Apple Desktop Bus system

594-687: The Mac with the original single-purpose mouse and keyboard ports, and no general-purpose system for low-speed devices to use. The first system to use Apple Desktop Bus was the Apple II GS of 1986. It was used on all Apple Macintosh machines starting with the Macintosh II and Macintosh SE . Apple Desktop Bus was also used on later models of NeXT computers. The vast majority of Apple Desktop Bus devices are for input, including trackballs , joysticks , graphics tablets and similar devices. Special-purpose uses included software protection dongles and even

627-581: The United States, the Federal Communications Commission oversees their use. Transceivers must meet certain standards and capabilities depending on their intended use, and manufacturers must comply with these requirements. However, transceivers can be modified by users to violate FCC regulations. For instance, they might be used to broadcast on a frequency or channel that they should not have access to. For this reason,

660-515: The address, the ID of one of the devices on the chain. The four bits allow for up to 16 devices on a single bus. The next two bits specify one of four commands, and the final two bits indicate one of four registers. The commands are: For instance, if the mouse is known to be at address $ D, the computer will periodically send out a 1-byte message on the bus that looks something like: 1101 11 00 This says that device $ D (1101) should talk (11) and return

693-480: The complexity of the data that can be broadcast, analog transceivers operate very reliably and are used in many emergency communication systems. They are also cheaper than digital transceivers, which makes them popular with the CB and HAM radio communities. Digital transceivers send and receive binary data over radio waves. This allows more types of data to be broadcast, including video and encrypted communication, which

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726-441: The contents of register zero (00). To a mouse this means "tell me the latest position changes". Registers can contain between two and eight bytes. Register zero is generally the primary communications channel. Registers one and two are undefined, and are generally intended to allow 3rd party developers to store configuration information. Register three always contains device identification information. The addresses and enumeration of

759-412: The devices are set to default values when reset. For instance, all keyboards are set to $ 2, and all mice to $ 3. When the machine is first powered on, the ADB device driver will send out talk commands asking each of these known default addresses, in turn, for the contents of register three. If no response comes from a particular address, the computer marks it dead and doesn't bother polling it later. If

792-408: The fairly sophisticated Zilog 8530 to supply serial communications. This was initially done to allow multiple devices to be plugged into a single port, using simple communication protocols implemented inside the 8530 to allow them to send and receive data with the host computer. The idea was to allow multiple devices to be connected to a port, eliminating the need for many different types of ports or

825-475: The host, the devices wait a short random time before responding, and then only do so after "snooping" the bus to make sure it was not busy. With two dongles plugged in, for instance, when the bus is first setting up and queries that address, one of them will be the first to respond due to the random wait timer. The other will notice the bus was busy and not respond. The host will then send out another message to that original address, but since one device has moved to

858-409: The opening of a soldered-in fuse on the motherboard. If brought to an authorised dealer, this can result in a motherboard swap at a significant expense. The simpler alternative is to obtain a fuse at a nominal cost and wire it in parallel across the open motherboard fuse (not necessarily requiring soldering ). Proprietary hardware Proprietary hardware is computer hardware whose interface

891-451: The receiving socket on a device such as a keyboard; various Apple keyboards use at least three of these possible orientations. The mini-DIN connector is only rated for 400 insertions and it is easy to bend a pin if not inserted with caution; in addition, the socket can become loose, resulting in intermittent function. Some Apple Desktop Bus devices lack a pass-through connector, making it impossible to daisy-chain more than one such device at

924-453: The same software. Those vendors were nicknamed plug compatible manufacturers (PCMs). This computer hardware article is a stub . You can help Misplaced Pages by expanding it . Transceiver Radio transceivers are widely used in wireless devices . One large use is in two-way radios , which are audio transceivers used for bidirectional person-to-person voice communication. Examples are cell phones , which transmit and receive

957-464: The similar PS/2 connector used in many PC-compatibles at the time, Apple Desktop Bus was rapidly replaced by USB as that system became popular in the late 1990s; the last external Apple Desktop Bus port on an Apple product was in 1999, though it remained as an internal-only bus on some Mac models into the 2000s. Early during the creation of the Macintosh computer, the engineering team had selected

990-465: The stop bit to indicate that a device requires a service request. Two of the other pins are used for +5 V power and ground. The +5 V pin guarantees at least 500 mA, and requires devices to use only 100 mA each. ADB also includes the PSW (Power Switch) pin which is attached directly to the power supply of the host computer. This is included to allow a keypress on the keyboard to start the machine without needing

1023-457: The two sides of a phone conversation using radio waves to a cell tower , cordless phones in which both the phone handset and the base station have transceivers to communicate both sides of the conversation, and land mobile radio systems like walkie-talkies and CB radios . Another large use is in wireless modems in mobile networked computer devices such laptops , pads, and cellphones, which both transmit digital data to and receive data from

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1056-457: The use of expansion slots . During development of this AppleBus system, computer networking became a vitally important feature of any computer system. With no card slots, the Macintosh was unable to easily add support for Ethernet or similar local area networking standards. Work on AppleBus was re-directed to networking purposes, and was released in 1985 as the AppleTalk system. This left

1089-412: Was not common, it is possible for the Apple Desktop Bus to have more than one device of the same sort plugged in — two graphics tablets or software copy protection dongles, for instance. In this case when it asks for devices on that default address, both will respond and a collision could occur. The devices include a small bit of timing that allows them to avoid this problem. After receiving a message from

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