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Automotive Remote Technology

Remote keyfobs for vehicles use several important technologies to accomplish what they do. Automotive Remotes are both computing devices and radio signal transmitters. And they utilize important encryption concepts to protect your security. While not the most complex devices among those you use every day, automotive remotes are complex. That is why Remotes Unlimited has assembled a skilled technical staff who understand critical aspects of the electronics, encryption and signal transmission features of our products. Our founder even holds a patent related to a touch-screen keyfob cloning device. When you shop on our site, you can be confident that Remotes Unlimited understands the car remotes  we are selling and will do everything in our power deliver not only a quality product but also expert technical service.

Signal Transmission

Nearly all car remotes send their signal via radio frequency transmission within a range of 275-450 MHz. (The exceptions to this rule typically use infra-red signals, but these are inferior because they require "line-of-sight" between the transmitter and the receiver.) Radio frequency devices are regulated in the US by the FCC (and by the IC in Canada), so each automotive remote designed undergoes a testing process and, when approved, then receives an FCC ID. Most keyfobs have the FCC ID printed either on the back of the case or somewhere inside. And, as it happens, this FCC ID is one of the best ways to identify exactly which car remote a customer has. The range of these signals varies by the type of key fob, but most signals are effective only to 100 yards or less.

Alarm Remote "Transceivers"

Aftermarket car alarm manufacturers - in an attempt to provide features not included on the keyless entry systems that increasingly are standard equipment on new vehicles - now market many car alarm systems that have two-way communications. In addition to sending remote instructions to the vehicle, these systems also send "feedback" information back to the remote key fob. This is useful for remote start systems, for which it is very useful to know if your press of the key fob button actually started the car that is sitting in the carport on an icy winter day. The remotes for these systems are called "transceivers" because they both transmit and receive signals. They usually have and LCD or OLED screen to display information. As a result of the added technology, two-way car alarm remote controls tend to be more fragile and more expensive.

Guts of a key fob: The Circuit Board

An automotive remote control is basically a case containing a circuit board (PCB), a battery and a button pad (sometimes called a bladder). The PCB has signal transmission electronics, sensors to detect when a button is pushed, an LED light to indicate that it is working, and most important, a memory chip with one or hundreds of thousands stored code numbers. When a button is pushed, the car remote begins transmission of a signal that includes some unique identification information followed by the code. For most remotes, this is all the device does.

Types of Automotive Remote Controls

There are many ways to classify car remotes, and thus many "types" of automotive remote controls.

Manufacturer-Installer - We consider who sold and installed a system when we talk about "factory keyless entry" (FKE) systems, "aftermarket alarm" (AA) systems and "dealer-installed" (DI) systems. The former are developed by the vehicle manufacturer and installed at the assembly plant. The latter are add-on systems sold and installed by alarm shops. The confusing thing is that automotive dealers also sell and install systems, and these systems either could be one developed by the vehicle manufacturer specifically for their nameplate vehicles or could be an aftermarket alarm system.

System functions - It gets even more confusing when the functions of the system are considered. Aftermarket system manufacturers tend to classify their products as (1) "keyless entry" (meaning the door locks can be controlled by a remote); (2) "remote start" (meaning the engine can be started from outside the vehicle); or (3) "anti-theft" (meaning the system has audible alarms, ignition shut-off, and/or other functions to deter theft). More recently, AA system manufacturers have sold "two-way" systems, for which the remote not only transmits instructions to the vehicle but also receives and displays vehicle status information back from the vehicle. Factory keyless entry systems were originally developed purely for remote door lock control and with a panic/car-finder feature, but many of these systems now also include remote start and anti-theft features.

Automotive Remote Transmitters - The first remote transmitters were all what we at RUI think of as a "keyfob". In this sense, a keyfob is solely a transmitter housed in a plastic case that one would attach to a keyring. Its sole function was to send some kind of remote instruction to a receiver in the vehicle - to turn an alarm system on or off, lock or unlock the doors, or start the engine. Most systems still use a keyfob of this description. However, during the past decade, some vehicle manufacturers started tweaking the basic concept. First, they combined the key with the remote, either in the form of a "keyhead" remote (which integrates the remote transmitter and buttons into a plastic housing that forms the traditional head of the key), or in the form of a "switchblade" remote (in which the key sits inside the remote case until it is flipped out by pressing an additional button on the remote). Even more recently, some vehicle manufacturers have made the key itself obsolete by simply putting a transponder in the remote to handle the key's security function and placing a push-button ignition switch in the vehicle. The keyfobs for these systems are typically referred to as "proximity remotes" or "smart keys". Not to be outdone with respect to innovation, some AA system manufacturers have taken the approach of doing away with the keyfob by enabling their systems to be controlled from a cell phone.

Transmitter / Security Technology - The final way in which RUI and most industry participants distinguish among types of automotive remote controls is via the form of remote transmission. The vast majority of automotive remotes use "radio-frequency" (RF) transmission, which places them under regulatory oversight by the FCC in the US and the IC in Canada. A small number of older remotes used "infra-red" (IR) transmission. A different technology distinction relates to what signal is being transmitted. First generation keyfobs broadcast a "fixed code" (meaning the same code was transmitted each time a button was pushed). Many first generation systems also had "fixed receiver" technology. For these systems, the receiver only responded to a single coded signal, meaning that replacement transmitters had to be adjusted or physically altered to transmit the single code that the receiver needed. Realizing the impracticality of fixed receivers, the industry later adopted "code learning" technology. For code learning systems, the receiver can be put into "programming" mode, which will then allow the system to accept the signal of a new transmitter, even if though the new transmitter sends a different coded signal than other remotes used with the system. Today, virtually all systems sold employ code-learning receivers. While fixed code transmitters were quite adequate in practice, security experts generated a scare by publicizing the fact that a remote's code could conceivably be copied, giving thieves access to the vehicle. (In practice, thieves have numerous means of getting inside a vehicle and very few, if any, ever resorted to copying a keyfob.) Responding to this perceived security risk, the industry developed a second generation coding approach referred to as "rolling code" or "code hopping". This technology, along with code learning receivers, is now used on virtually all new systems sold.

For more information, see the FAQs in "Buying a Remote"

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