Abstract: In some examples a printing system includes purging manifolds. The printing system includes a fluid ejection device to dispense a fluid and a first reservoir to house a fluid. The system further includes a purging manifold to fluidically couple to the fluid ejection device, and the purging manifold to fluidically couple to the first reservoir. The purging manifold includes a second reservoir. The purging manifold further includes a supply port; a fluid inlet port; and a purging outlet port. The purging outlet port is disposed above the supply port to convey fluid to the first reservoir. The printing system also includes a fluid interface connector to fluidically connect to the supply port and fluidically connect to the fluid ejection device.

Abstract: A method of recirculating printing fluid that includes with a first pump upstream of an internal reservoir, pumping printing fluid into the reservoir and with a second pump downstream of the internal reservoir and upstream of a pen assembly, pumping printing fluid from the reservoir.

Abstract: In one example in accordance with the present disclosure, a print fluid refill system is described. The print fluid refill system includes a reservoir to hold a volume of print fluid to be supplied to a printhead. The print fluid refill system also includes a pump to 1 ) draw print fluid from the reservoir via a reservoir line and 2) transport print fluid to a reserve tank via a reserve line. The print fluid refill system also includes the reserve tank to, during refill of the reservoir, supply print fluid to a printhead via a printhead line. The reserve tank supplies print fluid to the printhead when fluid is passed to the reservoir via a return line.

Abstract: An example of an apparatus is provided. The apparatus includes a current source. The apparatus includes a conductor in electrical communication with the current source and a conductive fluid in a reservoir. The apparatus includes a first sensing rod to extend into the reservoir, wherein the first sensing rod has a first diameter. The apparatus includes a tip disposed at an end of the first sensing rod to interact with a surface of the conductive fluid. The tip has a second diameter over a first portion of the tip adjacent to the first sensing rod. The second diameter is smaller than the first diameter. The apparatus includes a sensor to detect an electrical signal between the conductor and the first sensing rod.

Abstract: An example printing apparatus includes a reservoir to contain a printing agent. The printing apparatus further includes a recovery port to receive connection of a recovery vessel and to communicate flow of the printing agent from the reservoir to the recovery vessel during a recovery operation. The printing apparatus further includes a recovery pump to pump the printing agent from the reservoir through the recovery port to the recovery vessel during the recovery operation. The printing apparatus further includes a vacuum pump at the reservoir to reduce pressure in the reservoir to below atmospheric pressure during the recovery operation to draw unrecovered printing agent away from the recovery port when the recovery vessel is removed from the recovery port.

Abstract: In one example in accordance with the present disclosure, a fluid extraction system is described. The fluid extraction system includes an interface to fluidically and electrically couple a removable extraction reservoir to a printing device. A return line of the fluid extraction system is to connect the interface and a reservoir of the printing device. The fluid extraction system includes a switch to 1) responsive to attachment of the removable extraction reservoir to the printing device, open the return line to direct fluid form the reservoir to the interface and 2) responsive to removal of the removable extraction reservoir from the printing device, close the return line.

Abstract: Some examples include a print substance reservoir for a printing system including a housing to be arranged within a printing device, the housing having an interior for containing a print substance and an exterior, an active vent valve to allow gases to travel from the interior to the exterior when the inlet is receiving the print substance, the active vent valve electrically energizable and de-energizable in response to signals corresponding to the transfer of the print substance into the housing, a passive inlet valve to open to allow air to enter the interior during removal of the print substance from the reservoir, the passive inlet valve biased to a closed position, and a passive pressure relief valve to open when pressure within the interior is greater than a predetermined pressure limit, the passive pressure relief valve biased to a closed position.

Abstract: A printing device may include an input port to interface with a supply simulator; and a drain fluidic interface to interface with a removable extraction reservoir simultaneously with the coupling of the supply simulator with the input port; the supply simulator comprising a memory device to transfer data related to an amount of fluid transferred between the printing device and the removable extraction reservoir.

Abstract: In one example in accordance with the present disclosure, a fluid extraction system is described. The fluid extraction system includes an interface to fluidically and electrically couple a removable extraction reservoir to a printing device. A supply line of the fluid extraction system transports fluid from the interface to a reservoir of the printing device. A return line of the fluid extraction system is coupled to the reservoir and supply line and transports fluid from the reservoir to the interface. The fluid extraction system also includes a switch to, responsive to removal of the removable extraction reservoir from the printing device, activate a fill pump to draw fluid through the supply line away from the interface.

Abstract: An extraction pump of a printing device fluidically connected to a reservoir of the printing device is set to a specified rotational velocity. A pulse-width modulation (PWM) value of the extraction pump correspondingly increases until the extraction pump rotates at the specified rotational velocity. While the power of the extraction pump is monitored, a power of a supply pump of the printing device fluidically connected between the extraction pump and the reservoir is continually increased; the power of the extraction pump correspondingly decreases to maintain rotation of the extraction pump at the specified rotational velocity. Responsive to the power of the extraction pump decreasing to a characterized value for the specified rotational velocity, the power of the supply pump ceases being increased.

Abstract: An example printing apparatus includes a reservoir to contain a printing agent. The printing apparatus further includes a recovery port to receive connection of a recovery vessel and to communicate flow of the printing agent from the reservoir to the recovery vessel during a recovery operation. The printing apparatus further includes a recovery pump to pump the printing agent from the reservoir through the recovery port to the recovery vessel during the recovery operation. The printing apparatus further includes a vacuum pump at the reservoir to reduce pressure in the reservoir to below atmospheric pressure during the recovery operation to draw unrecovered printing agent away from the recovery port when the recovery vessel is removed from the recovery port.

Abstract: In example implementations, a storage apparatus is provided. The storage apparatus includes a sealed reservoir partially filled with a print agent. A float is partially submerged in the print agent. A weight is coupled to a submerged portion of the float. A vent is coupled to the float and an opening in the sealed reservoir. A valve is coupled to an unsubmerged portion of the float.

Abstract: In one example in accordance with the present disclosure, a fluid extraction system is described. The fluid extraction system includes an interface to fluidically and electrically couple a removable extraction reservoir to a printing device. A return line of the fluid extraction system is to connect the interface and a reservoir of the printing device. The fluid extraction system includes a switch to 1) responsive to attachment of the removable extraction reservoir to the printing device, open the return line to direct fluid form the reservoir to the interface and 2) responsive to removal of the removable extraction reservoir from the printing device, close the return line.

Abstract: A method of recirculating printing fluid that includes with a first pump upstream of an internal reservoir, pumping printing fluid into the reservoir and with a second pump downstream of the internal reservoir and upstream of a pen assembly, pumping printing fluid from the reservoir.

Abstract: In one example in accordance with the present disclosure, a fluid extraction system is described. The fluid extraction system includes an interface to fluidically and electrically couple a removable extraction reservoir to a printing device. A supply line of the fluid extraction system transports fluid from the interface to a reservoir of the printing device. A return line of the fluid extraction system is coupled to the reservoir and supply line and transports fluid from the reservoir to the interface. The fluid extraction system also includes a switch to, responsive to removal of the removable extraction reservoir from the printing device, activate a fill pump to draw fluid through the supply line away from the interface.

Abstract: A printing device may include an input port to interface with a supply simulator; and a drain fluidic interface to interface with a removable extraction reservoir simultaneously with the coupling of the supply simulator with the input port; the supply simulator comprising a memory device to transfer data related to an amount of fluid transferred between the printing device and the removable extraction reservoir.

Abstract: An example of an apparatus is provided. The apparatus includes a a current source. The apparatus includes a conductor in electrical communication with the current source and a conductive fluid in a reservoir. The apparatus includes a first sensing rod to extend into the reservoir, wherein the first sensing rod has a first diameter. The apparatus includes a tip disposed at an end of the first sensing rod to interact with a surface of the conductive fluid. The tip has a second diameter over a first portion of the tip adjacent to the first sensing rod. The second diameter is smaller than the first diameter. The apparatus includes a sensor to detect an electrical signal between the conductor and the first sensing rod.

Abstract: An extraction pump of a printing device fluidically connected to a reservoir of the printing device is set to a specified rotational velocity. A pulse-width modulation (PWM) value of the extraction pump correspondingly increases until the extraction pump rotates at the specified rotational velocity. While the power of the extraction pump is monitored, a power of a supply pump of the printing device fluidically connected between the extraction pump and the reservoir is continually increased; the power of the extraction pump correspondingly decreases to maintain rotation of the extraction pump at the specified rotational velocity. Responsive to the power of the extraction pump decreasing to a characterized value for the specified rotational velocity, the power of the supply pump ceases being increased.

Abstract: In one example in accordance with the present disclosure, a fluid extraction system is described. The fluid extraction system includes an interface to fluidically and electrically couple a removable extraction reservoir to a printing device. The removable extraction reservoir is to receive an amount of fluid from a reservoir in the printing device. The system also includes a controller to, based on data received from memory of an interfaced removable extraction reservoir, initiate an extraction operation wherein fluid from the reservoir is passed to the removable extraction reservoir.

Abstract: Some examples include a print substance reservoir for a printing system including a housing to be arranged within a printing device, the housing having an interior for containing a print substance and an exterior, an active vent valve to allow gases to travel from the interior to the exterior when the inlet is receiving the print substance, the active vent valve electrically energizable and de-energizable in response to signals corresponding to the transfer of the print substance into the housing, a passive inlet valve to open to allow air to enter the interior during removal of the print substance from the reservoir, the passive inlet valve biased to a closed position, and a passive pressure relief valve to open when pressure within the interior is greater than a predetermined pressure limit, the passive pressure relief valve biased to a closed position.