The entire line voltage is applied to the motor terminals via a direct on line (DOL) or across-the-line starter. This is the most basic kind of motor starter. If the high inrush current of the motor does not produce an excessive voltage drop in the supply circuit, a direct-on-line starter can be employed. Its advantage is that it requires less insulation around the wiring and can thus be installed closer to the motor.
A remote-start system uses a transmitter unit attached to the driver's car keychain or fob to communicate with an antenna mounted on the vehicle. The transmitter sends a signal through the ignition switch to start the engine. After driving for some time, the engine shuts itself off if the driver removes his or her foot from the gas pedal. The remote-start system may also include a battery charger connected in such a way that it charges the vehicle's battery while the engine is running.
Some modern vehicles are equipped with a global positioning system (GPS). The GPS allows the driver to find his or her location at any given time. Some global position systems can provide directions based on your current location. In addition, some newer models now include drive-by-wire technology that eliminates many of the mechanical components inside the car, such as steering wheels and gas pedals. These types of vehicles require electrical power to operate their electronic components. For example, they must have electricity to send signals to display information on LCD screens or to activate air bags when needed.
DOL indicates that the motor is connected directly ON-LINE with a single contactor and no beginning circuit to reduce the high starting current. The Delta component of Star-Delta. Star-Delta employs two contactors, one for starting at a lower voltage in the Star configuration and another for running at a greater voltage in the Delta configuration. The second contactor is activated by a semiconductor switch called an "electromechanical relay" (EMR). EMRs are used instead of hard-wired connections to control motors larger than about 150 volts DC. EMRs can be reprogrammed from a remote location using radio frequency (RF) signals, which allows maintenance personnel to make changes without going inside the machine.
Direct On Line (DOL) systems have one advantage over starter-generator sets for small motors: there's no need for a battery. However, they have one major disadvantage: they require a full load be applied to start them. If you only need to run a sensor or two when the system is installed, a SG set is far more efficient. Direct On Line systems also require a separate contactor for each phase, while a three-wire starter generator set requires only one contact closure to start all three phases. Direct On Line systems are therefore less flexible than three-phase systems.
The term "star delta" is often used as a catchall term for any type of split-system motor controller.
This design's flexibility may also be utilized to start the motor at a lower voltage. Star-delta connections provide a low beginning current that is roughly one-third that of direct-on-line starting. Star-delta starters are ideal for high inertia loads, when the load is initiated after reaching full load speed. They are less efficient than pure resistive starters at low speeds when both coils are drawing current.
The disadvantage of this type of starter is that if either coil should fail then the entire output of the starter is lost. Also, each coil has its own breaker or fuse within it so if either one blows you have failed starting anyway. Finally, these starters are not suitable for applications where overcurrent protection is required since they do not include any form of protective device within them. They can still be used in small appliances such as hair dryers and curling irons though.
Star-delta starters use two silicon controlled rectifiers (SCRs) instead of one. One SCR controls the flow of current into the motor from the battery, while the other controls the flow of current out of the motor back to the battery. Since there are two circuits involved, two breakers or fuses must be used to protect against failure of either one. These starters are more complex than pure resistive starters but less expensive to produce. They are commonly used in small appliance motors.
They do, however, diminish beginning torque by around 33%. Direct-on-line starters produce much higher initial torque and can handle non-ideal loads more effectively than star-delta starters.
Direct Inward Dialing (DID) is when a telephone service provider connects a block of telephone numbers to your company's private branch exchange (PBX). It allows businesses to set up virtual numbers that can bypass the main reception lines and go directly to a desk extension or group of extensions. This can be useful if you have multiple locations or employees working from home.
When you order DID services, your phone company will connect your incoming calls first to one of their offices or agents. If the agent knows who is calling, they will connect the call straight through to an available number. Otherwise, the call is placed in a queue until an office is free to take it.
This service is ideal for companies that have several different departments that may need to reach each other occasionally but don't want to pay for a separate line for each person or team.
Most phone companies charge between $5 and $10 per month for this service. Some providers will charge more if you call outside of your local area code or if you request specific numbers be blocked.
You should ask your phone company how DID services work before you sign up for them so there are no surprises later on. They should be able to explain everything there is to know about DID, including any fees that may apply.
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Direct Inward Calling is utilized when your PBX telco connection permits direct dialing to extensions within a PBX via shared physical lines (or channels on a PRI). Before connecting each call, the DID service identifies the "called party" by DTMF or other digital techniques. The carrier then connects the call to the correct extension.
DID is most commonly used for extending office services to remote offices or providing internal phone numbers for employees who are not assigned desk phones. It is also useful for making long distance calls that are billed to the company account.
Companies can reduce their long-distance bills by as much as 80% by using DID for some of their remote locations. Because there is no charge for local calls, companies have an incentive to keep their remote offices connected.
DID devices connect your off-premise telephone lines directly to your in-house phone system. They provide a cost-effective alternative to public switch carriers for businesses with several remote offices or employees living in different cities.
Because DID uses existing inside wiring for its connections, it is preferable for companies with many branch offices or whose offices are located in older buildings. This type of service is also recommended for companies that want to save money while still providing voice mail access to their employees.
DID services are offered by most major telcos and some smaller providers.