*****THIS IS A COMBINED SOURCES SOUGHT NOTICE AND NOTICE OF INTENT TO SOLE SOURCE***. BACKGROUND The Fundamental Thermodynamics group at the Sensor Science Division is conducting Photonic ac-dc Thermal Transfer Standard (PTTS) project. The main focus of the project is to develop the next-generation chip-scale photonic ac-dc difference metrology that can replace legacy thin-film multijunction thermal converters (MJTCs), reduce the ac-dc difference calibration chain and sensor ownership cost. The PTTS project, pursued by the Fundamental Thermodynamics group is part NIST-on-a-Chip (NOAC) program. The timely achieving project's milestones is NIST-mission-critical task and is one of the priorities of the Physical Measurement Laboratory (PML). One of the essential milestones of Photonic ac-dc Thermal Transfer Standard (PTTS) is to develop high‑precision, deployable photonic readout system. This capability is a critical milestone of the PTTS project, providing the accuracy and stability needed to advance photonics-based ac-dc difference metrology toward practical implementation. To achieve these essential for the project milestones, the Fundamental Thermodynamics group has a critical need for one (1) high-seed lock-in/servo system. This instrument is essential for enabling scalable and practical solutions for next-generation ac-dc difference metrology. Delaying or not approving this procurement would directly hinder progress on key deliverables of the NOAC Photonic ac-dc Thermal Transfer Standard (PTTS) project. Timely acquisition is essential to ensure technical objectives are met and the project remains on track to deliver transformative advances in next‑generation ac-dc difference metrology. NIST is seeking information from sources that may be capable of providing high-speed lock-in/servo system to support NOAC Photonic ac-dc Thermal Transfer Standard (PTTS) project. If no alternate sources are identified, the Government intends to issue a Sole Source Award to, Liquid Instruments Inc. (UEI MS6AHD4EF8D7:) under the authority of FAR 12.102(b) The North American Industry Classification System (NAICS) code for this acquisition is 334516. The high-speed lock-in/servo system must meet the following minimum specifications: Shall include at least 4 Analog inputs with a Bandwidth of at least 600 MHz (for up to 2 channels being in use) and at least 300 MHz (for up to 4 channels being in use) Shall have a sampling rate of at least 1 GSa/s per1 channel Shall have an ADC Resolution of at least 10-bit with a preference for 18 bit or higher. Maximum voltage range 40 Vpp Input Impedance 50 Ω or 1 MΩ Input coupling AC or DC Input voltage noise less than 30 nV√Hz at 100 Hz Input reference noise shall be no greater that 500 µV root-mean-square (RMS) Shall have at least 4 analog outputs channels Output bandwidth with at least 100 MHz with at least +/- 5 volts, and at least 500 MHz with at least +/- 1 volts Output sampling rate of at least 1…