Sets the source current level for the supply. In the example, it is used to configure the output current before saving a setup.
| Name | Type | Values | Description |
|---|---|---|---|
| current | real | A | Current level to set. |
SOURCE:CURR 1.6A
SCPI COMMAND REFERENCE
The Keithley 2200-60-2 is Keithley's power supply in the Series 2200 Programmable DC Power Supply family. Its SCPI remote-control interface exposes 101 commands across 18 subsystems - 77 settable and 24 queries - and every command is documented here with its parameters, accepted values, return format, and a copy-paste PyVISA example for automating test and measurement.
101
Commands
77
Settable
24
Queries
18
Subsystems
SCPI
1991.0
Verified
2026-07-16
Sets the source current level for the supply. In the example, it is used to configure the output current before saving a setup.
| Name | Type | Values | Description |
|---|---|---|---|
| current | real | A | Current level to set. |
SOURCE:CURR 1.6A
Sets the source function mode to fixed output for the configured setup example.
| Name | Type | Values | Description |
|---|---|---|---|
| mode | enum | FIX | Source function mode. |
SOURCE:FUNC:MODE FIX
Sets the source voltage for the output. The example shows setting the voltage to 3.33 V.
| Name | Type | Values | Description |
|---|---|---|---|
| voltage | real | V | Voltage to set at the source output. |
SOURCE:VOLT 3.33V
Sets the list output count used by the configured source list.
| Name | Type | Values | Description |
|---|---|---|---|
| count | integer | 1 | Number of list output steps to execute. |
SOURCE:LIST:COUT 2
Sets the current value for an entry in the list configuration. The example shows indexed current entries such as `SOURCE:LIST:CURR 1, 5A`.
| Name | Type | Values | Description |
|---|---|---|---|
| index | integer | 1 - 5 | List step number to configure. |
| current | real | A | Current value for the selected list entry. |
SOURCE:LIST:CURR 1, 5A SOURCE:LIST:CURR 2, 5A SOURCE:LIST:CURR 3, 1A SOURCE:LIST:CURR 4, 3A SOURCE:LIST:CURR 5, 1A
Sets the list mode for the configured source list.
| Name | Type | Values | Description |
|---|---|---|---|
| mode | enum | CONT | List mode selection. |
SOURCE:LIST:MODE CONT
Saves the configured list to a storage location or memory slot. The example saves the list as 3.
| Name | Type | Values | Description |
|---|---|---|---|
| location | integer | - | Storage location or list number to save to. |
SOURCE:LIST:SAV 3
Sets the list step count used when configuring a sequence list.
| Name | Type | Values | Description |
|---|---|---|---|
| count | integer | 1 | List step count. |
SOURCE:LIST:STEP 5
Sets a voltage value in the source list at the specified list index. The example shows list entries written as index, value pairs with units.
| Name | Type | Values | Description |
|---|---|---|---|
| index | integer | - | List position to configure. |
| voltage | real | V | Voltage value for the specified list entry. |
SOURCE:LIST:VOLT 1, 2V SOURCE:LIST:VOLT 2, 5V SOURCE:LIST:VOLT 3, 1V SOURCE:LIST:VOLT 4, 3V SOURCE:LIST:VOLT 5, 7V
Sets the width for each entry in the source list. The manual shows it being used with an index and a time value.
| Name | Type | Values | Description |
|---|---|---|---|
| index | integer | 1 - 5 | List entry number to configure. |
| width | real | 0.001 | Width time for the specified list entry. |
SOURCE:LIST:WIDTH 1, 0.001S SOURCE:LIST:WIDTH 2, 0.001S SOURCE:LIST:WIDTH 3, 1S SOURCE:LIST:WIDTH 4, 0.001S SOURCE:LIST:WIDTH 5, 0.001S
Turns the output on or off.
| Name | Type | Values | Description |
|---|---|---|---|
| state | enum | ON | OFF | Sets the output state. |
OUTPUT:STATE ON
Sets the timer delay for the output timer feature. The example configures a delay of 7 seconds before the output automatically turns off.
| Name | Type | Values | Description |
|---|---|---|---|
| delay | real | s | Time delay before the output turns off. |
OUTPUT:TIMER:DELAY 7S
Enables or disables the output timer feature. When enabled, the output timer is used together with the timer delay to automatically turn the output off after the programmed interval.
| Name | Type | Values | Description |
|---|---|---|---|
| state | enum | ON | OFF | Turns the output timer feature on or off. |
OUTPUT:TIMER:STATE ON OUTPUT:TIMER:STATE OFF
Associates the rear-panel DFI TTL output with a specified bit in the status byte register. Once associated, the DFI signal reflects the state of the selected bit; the port must be in DFI or RI mode before using this command.
| Name | Type | Values | Description |
|---|---|---|---|
| mode | enum | OFF | QUES | OPER | ESB | RQS | Selects which status byte register bit the DFI output reflects. |
OUTput:DFI:SOURCE QUES
Configures whether the power supply powers up with the output off or returns the output to the state it was in when power was removed.
| Name | Type | Values | Description |
|---|---|---|---|
| mode | enum | RST | RCL0 | Selects the power-up output state. |
OUTPUT:PON RST OUTPUT:PON? might return RCL0, which would indicate that the instrument will return to the present output state if the power is cycled.
Clears a protection trip condition caused by over voltage, over temperature, or remote inhibit.
OUTP:PROT:CLE
Sets the input mode of the RI (remote inhibit) input pin. The command is effective only when the rear panel TTL input and output are configured in RI/DFI mode using [SOURce:]DIGital:FUNCtion.
| Name | Type | Values | Description |
|---|---|---|---|
| mode | enum | OFF | LATChing | LIVE | Selects the RI input mode. |
OUTP:RI:MODE LATC OUTP:RI:MODE? might return OFF, which would indicate that remote inhibit is not controlling the output of the instrument.
Turns the power supply output channel on or off.
| Name | Type | Values | Description |
|---|---|---|---|
| state | enum | 0 | 1 | ON | OFF | Selects whether the output is on or off. |
Sets the duration of the output timer. When the timer is active, the power supply output turns off automatically if left on longer than the specified duration.
| Name | Type | Values | Description |
|---|---|---|---|
| duration | real | 0.01 - 60000 | Timer duration to set, as a flexible decimal time value with units S or ms. |
| qualifieropt | enum | MIN | MAX | DEF | Sets the timer duration to the minimum, maximum, or default value. |
OUTP:TIM:DEL MIN OUTP:TIM:DEL? might return 60.2, which would represent the maximum time, in seconds, that the output of the instrument could be turned on if the timer is active.
Turns the output timer function on or off. When activated and a duration is set, the supply output turns off automatically if left on longer than the specified duration.
| Name | Type | Values | Description |
|---|---|---|---|
| state | enum | 0 | 1 | ON | OFF | Turns the output timer off or on. |
OUTPUT:TIMER:STATE ON OUTPUT:STATE ON OUTPUT:TIMER:STATE OFF
Turns the power supply output on or off. The example shows the command being used to turn the output on with a value of 1.
| Name | Type | Values | Description |
|---|---|---|---|
| state | enum | 0 | 1 | Output state. |
OUTPUT 1
Sets the trigger source to BUS. The manual’s example shows it used as a programming command.
TRIGGER:SOURCE:BUS
Forces an immediate trigger event.
TRIGGER
Sets the source of trigger events.
| Name | Type | Values | Description |
|---|---|---|---|
| source | enum | MANual | IMMediate | EXTernal | BUS | Selects the trigger source. |
TRIGGER:SOURCE BUS
Configures trigger-related settings as shown by the examples, which use TRIGGER:SOURCE BUS before running a list and TRIGGER IMMEDIATE to start it. The slice does not document any dedicated parameters or query return for the bare :TRIGGER mnemonic.
TRIGGER:SOURCE BUS TRIGGER IMMEDIATE
Immediately initiates the selected trigger action. In the examples, it starts execution of the configured list when the instrument is in list mode and output is on.
TRIGGER IMMEDIATE TRIGGER:IMMEDIATE
Sets the trigger source used by the instrument. The examples show it being set to BUS before running a list.
| Name | Type | Values | Description |
|---|---|---|---|
| source | enum | BUS | Trigger source selection. |
TRIGGER:SOURCE BUS
Clears all event registers and queues.
Restores the state of the power supply from a copy of its settings stored in setup memory. The settings are stored using the *SAV command; if the specified setup memory is deleted, the command causes an error.
| Name | Type | Values | Description |
|---|---|---|---|
| NR1 | integer | 0 - 40 | Specifies the location of setup memory. |
*RCL 3
Saves the current state of the power supply into a specified nonvolatile memory location, overwriting any settings previously stored there. The saved state can later be restored with *RCL.
| Name | Type | Values | Description |
|---|---|---|---|
| location | integer | 1 - 40 | Nonvolatile memory location to save the state into. |
*SAV 2
Generates a trigger event.
*TRG
Initiates a self-test and reports any errors.
Prevents the instrument from executing further commands or queries until all pending commands are complete.
*WAI
Queries the instrument identification string. The example shows sending `*IDN?` and reading back the response.
*IDN?
Resets the power supply.
*RST
Sets the Operation Complete bit in the Standard Event Status Register when all pending operations have completed. This bit is used to indicate that an operation complete event has occurred.
Returns the Master Status Summary (MSS), which summarizes the OSB, ESB, MAV, QSB, and EQS bits in the SBR.
Sets the bits in the event status enable register (ESER). Use *ESE? to read the register.
| Name | Type | Values | Description |
|---|---|---|---|
| value | integer | 0 - 255 | Bit pattern written to the event status enable register. |
Reads the event status enable register (ESER).
Sets the service request enable register (SRER). The register controls which bits in the status byte register generate a Service Request and are summarized by the master status summary (MSS) bit.
Reads the service request enable register (SRER). The register controls which status byte bits generate a Service Request and are summarized by the master status summary (MSS) bit.
Controls how the enable registers are initialized at power-on. Sending *PSC 1 resets the enable registers to their default power-on settings, while *PSC 0 preserves their values through a power cycle.
| Name | Type | Values | Description |
|---|---|---|---|
| state | integer | 0 - 1 | Selects whether enable registers are reset at power-on or retained in nonvolatile memory. |
Reads the Standard Event Status Register (SESR) and summarizes pending events. Reading *ESR? empties the SESR and makes summarized events available to the Event Queue.
Turns the key beep sound on or off.
| Name | Type | Values | Description |
|---|---|---|---|
| state | enum | 0 | 1 | ON | OFF | Selects whether the key beep sound is turned off or on. |
CONF:SOUN:OFF CONF:SOUN? might return 0, indicating the key beeper is turned off.
Returns the last measured output current stored in the communications buffer of the power supply. A new measurement is not initiated by this command.
Returns the last measured output voltage stored in the power supply communications buffer. A new measurement is not initiated by this command.
FETC:VOLT? might return 5.0011, which would be the measured voltage across the power supply outputs in volts.
Returns the last measured output power stored in the communications buffer. A new measurement is not initiated by this command; the instrument updates the power calculation approximately every 100 ms.
FETCh:POW? might return 6.01667, which would be the power measured at the output of t he power supply in watts.
Initiates and executes a new current measurement, then returns the measured output current of the power supply.
MEAS:CURR? might return 0.09998, which would be the measured current on the output of the power supply in amperes.
Initiates and executes a new voltage measurement, then returns the measured output voltage of the power supply.
MEAS:VOLT? might return 5.0011 which would be the voltage measured across the power supply output in volts.
Queries the power supply for the measured output voltage.
MEASURE:VOLTAGE?
Measures the output current and returns the current reading.
MEASURE:CURRENT?
Sets the power supply current value in amperes or milliamperes. The minimum, maximum, or default current can also be selected with the MIN, MAX, or DEF keywords.
| Name | Type | Values | Description |
|---|---|---|---|
| current | real | A | Current value to set, expressed as a flexible decimal with units of mA or A. |
| qualifieropt | enum | MIN | MAX | DEF | Selects the minimum current, maximum current, or default current level. |
CURR 3A CURR 30mA CURR MIN
Sets the output current to the specified value. The example shows using the command with an amperes suffix.
| Name | Type | Values | Description |
|---|---|---|---|
| current | real | A | Output current value to set. |
CURRENT 0.1A CURRENT %f
Sets the rear-panel TTL control output state and queries the rear-panel TTL control input state. The command is enabled when the port mode is DIGITAL.
| Name | Type | Values | Description |
|---|---|---|---|
| state | integer | 0 - 1 | Sets the binary state of the rear-panel TTL control output to low or high, respectively. |
DIGITAL:DATA ON DIGITAL:DATA? might return 3, which would indicate that the TTL control input is high and the output is also high.
Sets or queries the function of the TTL control lines on the rear panel of the power supply. *RST value is TRIGger.
| Name | Type | Values | Description |
|---|---|---|---|
| mode | enum | TRIGger | RIDFi | DIGital | Selects the TTL control line function. |
DIGITAL:FUNCTION TRIGGER DIG:FUNC? might return RIDF, which would indicate that the TTL input and output are configure to function as remote inhibit and discrete fault input respectively.
Sets the function mode to fixed or list mode. In fixed mode the supply responds to discrete commands; in list mode it operates in list mode.
| Name | Type | Values | Description |
|---|---|---|---|
| mode | enum | FIXed | LIST | Selects fixed mode or list mode. |
[SOURCE:]FUNCTION:MODE LIST
Sets the instrument function mode. The examples show it being used to place the instrument in LIST mode.
| Name | Type | Values | Description |
|---|---|---|---|
| mode | enum | LIST | Selects the function mode. |
FUNCTION:MODE LIST
Configures the number of times the active list will execute before stopping.
| Name | Type | Values | Description |
|---|---|---|---|
| count | integer | 2 - 65535 | Number of times the active list will execute. |
| mode | enum | ONCe | REPeat | Special count modes: ONCe executes once and stops; REPeat loops continuously. |
Sets the current for a list step in units of A or mA. The query returns the current setting in amperes for the specified step.
| Name | Type | Values | Description |
|---|---|---|---|
| step | integer | 1 - 80 | Step number in the active list. |
| current | real | 0 - nameplate current rating | Current setting for the list step. |
[SOURce:]LIST:CURRent[:LEVel] <NR1>,<current> [SOURce:]LIST:CURRent[:LEVel]? <NR1>
Determines the power supply's response to a trigger in list mode.
| Name | Type | Values | Description |
|---|---|---|---|
| mode | enum | CONTinuous | STEP | Sets whether the power supply executes the entire list on each trigger or one step per trigger. |
LIST:MODE CONT LIST:MODE? might respond with STEP to indicate that the active list is configured to wait for one trigger for each step.
Recalls a previously saved list from the specified storage location and makes it the active list for editing or execution.
| Name | Type | Values | Description |
|---|---|---|---|
| NR1 | integer | 1 - 8 | List storage location to recall. |
LIST:RCL 5 would make the list stored in location 5 the active list for editing or execution.
Saves the active list file to a storage location in non-volatile memory.
| Name | Type | Values | Description |
|---|---|---|---|
| NR1 | integer | 1 - 8 | List storage location. |
LIST:SAV 4 saves the active list in list storage location 4.
Configures the number of steps in the active list. The number of steps must be set before loading the step voltage levels, current levels, and/or durations.
| Name | Type | Values | Description |
|---|---|---|---|
| count | integer | 2 - 80 | Number of steps to be configured in the list. |
| qualifieropt | enum | MIN | MAX | Use MIN or MAX to set the minimum or maximum allowed number of steps. |
Sets the voltage level of a specified step in a list, in units of V or mV.
| Name | Type | Values | Description |
|---|---|---|---|
| step | integer | 1 - 80 | Step number in the active list. |
| voltage | real | V or mV | Voltage level for the step, specified as a flexible decimal with units. |
LIST:VOLT 1, 3V
Sets the duration of a specified step in a list. The command accepts either a duration value with units of s or ms, or the keywords MIN or MAX.
| Name | Type | Values | Description |
|---|---|---|---|
| step | integer | 1 - 80 | Step number in the active list. |
| duration | real | s|ms | Time duration of the step. |
| qualifieropt | enum | MIN | MAX | Keyword alternative to a numeric duration. |
LIST:WIDTH 12, 100ms LIST:WIDTH? 12 might return 0.1, which would be the duration of step 12.
Sets how many times a list executes in list mode. The examples show values of ONCE and a numeric count.
| Name | Type | Values | Description |
|---|---|---|---|
| count | enum | ONCE | Number of times the list executes. |
LIST:COUNT ONCE LIST:COUNT 20
Sets the current level for a step in the list. The command is used with a step index and current value in a list sequence.
| Name | Type | Values | Description |
|---|---|---|---|
| step | integer | - | List step number to configure. |
| current | real | A | Current value for the specified list step. |
LIST:CURRENT 1,1.0A LIST:CURRENT 2,1.0A LIST:CURRent 1,1.0A LIST:CURRent 2,1.0A
Sets the current value for a step in a list program. The command is used in list mode sequences to define per-step current alongside voltage and width.
| Name | Type | Values | Description |
|---|---|---|---|
| step | integer | 1 | List step number to configure. |
| current | real | A | Current value for the specified list step. |
LIST:CURRENT 1,1.0A LIST:CURRent 1,1.0A
Sets the list operating mode. The examples show it being set to CONT before saving and running a list.
| Name | Type | Values | Description |
|---|---|---|---|
| mode | enum | CONT | List mode. |
LIST:MODE CONT
Saves the configured list in the specified location.
| Name | Type | Values | Description |
|---|---|---|---|
| location | integer | 1 | Storage location for the list. |
LIST:SAVE 1
Sets the number of steps in the list. The examples show it used with values such as 2 and 3.
| Name | Type | Values | Description |
|---|---|---|---|
| count | integer | - | Number of steps in the list. |
LIST:STEP 3 LIST:STEP 2
Sets the voltage for a specified list step. The examples show the step index followed by the voltage value with units.
| Name | Type | Values | Description |
|---|---|---|---|
| step | integer | - | List step number to configure. |
| voltage | real | V | Voltage value for the selected step. |
LIST:VOLT 1,2V LIST:VOLTAGE 1,5V LIST:VOLTAGE 2,5.5V
Sets the voltage for a step in a list program. The examples show it used with a step index and a voltage value with units.
| Name | Type | Values | Description |
|---|---|---|---|
| step | integer | - | List step index to configure. |
| voltage | real | V | Voltage value for the specified list step. |
LIST:VOLTAGE 1,5V LIST:VOLTAGE 2,5.5V
Sets the width of a list step. The examples show it used with a step index and a time value.
| Name | Type | Values | Description |
|---|---|---|---|
| step | integer | - | List step index to configure. |
| width | real | s | Width of the specified list step. |
LIST:WIDTH 1,5s LIST:WIDTH 2,10s LIST:WIDTH 3,2s
Sets the voltage value of the power supply. The command accepts a numeric voltage with units, or the keywords MIN, MAX, or DEF.
| Name | Type | Values | Description |
|---|---|---|---|
| voltage | real | 0 - the maximum nameplate voltage of the power supply | Voltage setting in volts; flexible decimal value with units V, mV, or kV. |
| qualifieropt | enum | MIN | MAX | DEF | Selects the minimum level, maximum level, or default level. |
VOLTAGE:MIN VOLTAGE? might return 1.05, which would be the voltage setting in volts.
Sets the over voltage protection (OVP) threshold level. The level can be set to a voltage value, or with the MIN, MAX, or DEF keywords.
| Name | Type | Values | Description |
|---|---|---|---|
| voltage | real | 0 - maximum OVP level | OVP threshold voltage. |
| qualifieropt | enum | MIN | MAX | DEF | Sets the OVP level to the minimum, maximum, or default level. |
VOLT:PROT 30V VOLT:PROT? might return 30, which would be the OVP threshold in volts.
Activates, deactivates, or checks the status of overvoltage protection (OVP).
| Name | Type | Values | Description |
|---|---|---|---|
| state | enum | 0 | 1 | OFF | ON | Sets the overvoltage protection state. |
VOLT:PROT:STAT 1 VOLT:PROT:STAT? might return 1, which would indicate that overvoltage protection is active.
Limits the maximum voltage that can be programmed on the power supply. It corresponds to the front-panel Max Voltage setting under the Protection submenu and is different from OVP because it cannot turn the output off.
| Name | Type | Values | Description |
|---|---|---|---|
| voltage | real | 0 - maximum nameplate voltage | Maximum output voltage limit to program. |
| qualifieropt | enum | MIN | MAX | DEF | Sets the voltage limit to the minimum, maximum, or default value. |
VOLT:RANG 3.2V VOLT:RANG? might return 3.2, which would be the maximum programmable voltage in volts.
Sets the output voltage of the power supply. The example shows both the long and short forms used with a numeric value in volts.
| Name | Type | Values | Description |
|---|---|---|---|
| voltage | real | V | Output voltage to set. |
VOLTAGE 3V VOLT 5.0
Returns the contents of the operation event register (OEVR) as a decimal integer. After execution, the operation event register is reset.
STATUS:OPERATION:EVENT? might return 10, which indicates that the power supply is waiting for trigger and is in a constant current mode.
Returns the contents of the questionable condition register (QCR). The return is a decimal integer representation of the register contents, ranging from 0 to 255.
STATUS:QUESTIONABLE:CONDITION? might return 1, which would indicate an over voltage condition.
Returns the contents of the questionable event register (QEVR). After execution, the register is reset.
STATUS:QUESTIONABLE:ENABLE 8 STATUS:QUESTIONABLE:ENABLE? might return 8, which would indicate that only a transition of the Remote Inhibit bit of the QCR would affect the QUES bit of the Status Byte Register.
Sets the negative transition filter of the questionable event register. The filter causes the corresponding bit in the questionable event register to become 1 when the questionable condition register transitions from 1 to 0.
| Name | Type | Values | Description |
|---|---|---|---|
| mask | integer | 0 - 255 | Binary bits of the Questionable NTR register are set according to this value. |
STATUS:QUESTIONABLE:NTRANSITION 8 STATUS:QUESTIONABLE:NTRANSITION? might return 8, which would indicate that a negative transition on the Remote Inhibit bit of the questionable condition register would be registered as an event.
Sets the positive transition filter of the questionable event register. The filter contents determine when the corresponding bit in the questionable event register becomes 1 as the questionable condition register transitions from 0 to 1.
| Name | Type | Values | Description |
|---|---|---|---|
| mask | integer | 0 - 255 | Binary bit mask applied to the questionable PTR register. |
STATUS:QUESTIONABLE:PTRANSITION 8 STATUS:QUESTIONABLE:PTRANSITION? might return 8 which would indicate that a positive transition on the Remote Inhibit bit of the questionable condition register would be registered as an event.
Returns the Operation Condition Register value. The example uses bit 5 of this register to determine whether a list is still running.
STATus:OPERation:CONDition?
Sets the bits in the operation enable register (OENR). The query form reads the contents of the OENR.
Reads the contents of the operation enable register (OENR). The OENR bits control whether the operation status bit (OSB) in the SBR is set when the corresponding event occurs.
Sets the bits in the Questionable enable register (QENR). The QENR bits are defined the same as bits 0 through 7 in the QEVR register and control whether the QSB in the SBR is set when a corresponding event occurs.
Reads the contents of the Questionable enable register (QENR).
Queries the power supply error code and error information, returning both values. See the messages and codes appendix for the meaning of the code and text.
SYSTEM:ERROR? might return 110, which means No Input Command to parse.
Simulates a front-panel button press when the instrument is in local mode. The command uses an integer key code corresponding to a front-panel button.
| Name | Type | Values | Description |
|---|---|---|---|
| NR1 | integer | 1 - 64 | Integer key code for the front-panel button to simulate. |
SYSTEM:KEY 64 would simulate a press of the Shift key.
Sets the power supply for control from the front panel.
SYS:LOC
Determines how the power supply initializes when its power switch is turned on. It can be configured to power up with default settings or restore the settings that were in effect when it was turned off.
| Name | Type | Values | Description |
|---|---|---|---|
| mode | enum | RST | RCL0 | Selects default settings after a power cycle or restores the most recent settings. |
SYST:POS RST SYSTEM:POSETUP? might respond with RST, which would indicate that the power supply is configured to restore the power supply to default settings when it powers up.
Sets the power supply to remote control mode.
SYSTEM:REMOTE
If the power supply is in remote mode, this command locks out the front panel LOCAL button. It has no effect when the instrument is in local mode.
SYSTEM:RWLOCK
Returns the SCPI version of the instrument. The returned value is the software version of the power supply as an <NR2> number.
SYSTEM:VERSION? might return 1991.0, which is the SCPI version number.
Puts the power supply into remote control mode.
SendSCPI("SYSTEM:REMOTE");Sets the output voltage. The example shows using `VOLT` with a numeric value to set the power supply output voltage.
| Name | Type | Values | Description |
|---|---|---|---|
| voltage | real | V | Output voltage to set. |
VOLT %f
Reads all event numbers from the Event Queue with a text description of each event. Reading an event removes it from the queue.
Reads the next event from the Event Queue. This query returns only the event number, and reading an event removes it from the queue.
Reads the next event from the Event Queue and returns the event number together with a text description of the event. Reading an event removes it from the queue.