Condition: Used — Tested and fully functional. Excellent condition with minimal usage. The unit was verified in-house showing: Almanac Status OK, correct time, phase lock achieved, Oscillator Mode 4, and 5 satellites acquired. Reference testing confirmed a clean 10.000 MHz (100.00 ns) output signal, yielding excellent results even under less than ideal test conditions.

Included in the sale:
• Spectrum Instruments TM4-M+ Rubidium Time Frequency Reference System (Part No. 21351-102)
• GPS antenna with cable
• USB cable (JDSU P/N 21130024)
• Coaxial cables (various types, including JDSU P/N 80-30662-01)
• BNC and RF adapters
• USB adapter
• Power cable
• Soft carry case (JDSU branded)

The images provided are of the actual item you will receive. Please review them carefully for the cosmetic condition and what is included in the sale.

The Spectrum Instruments TM4-M+ is a Rubidium Time and Frequency Reference System designed for precision synchronisation, frequency calibration, and distribution in laboratory, telecoms, and field environments. The unit combines a rubidium atomic oscillator with GPS receiver disciplining to deliver a highly accurate, traceable reference output with excellent short- and long-term stability.

The GPS-disciplined rubidium oscillator ensures the output remains locked to UTC, making it suitable for standards laboratories, calibration benches, communications test systems, and any application requiring a traceable 10 MHz reference signal. The system is capable of maintaining phase lock even in challenging GPS reception environments, and the portable design with integrated carry case makes it equally suited for field deployment.

Key Specifications:
Model: TM4-M+
Part Number: 21351-102
Oscillator Type: Rubidium atomic oscillator
Frequency Output: 10 MHz
Disciplining: GPS receiver (UTC-traceable)
Operating Modes: Multiple oscillator modes including GPS-disciplined lock
Interface: USB
Portability: Field-portable with soft carry case
Application: Calibration, synchronisation, telecoms testing, standards laboratory

Please refer to the manufacturer website for full specifications.

Shipping & Returns Policy

Shipping Policy

• Processing Time: Orders are typically processed and dispatched within 1 business day.
• Shipping Methods: We offer Expedited Shipping to all destinations using UPS/DHL/Fedex/Royal Mail and other reputable carriers.
• Shipping Times: Mainland UK: 1-2 Business Days / Mainland Europe and USA: 2-3 Business Days / Rest of the World 5-7 Business Days.
• Shipping Costs: These are calculated at checkout based on the shipping method, destination and package dimensions.
• CUSTOMS AND TAXES: It is YOUR responsibility to liaise with customs in your country and ensure your package is cleared and any taxes are paid.
• Shipping Destinations: We ship worldwide.
• Tracking: Once your order is shipped, we will provide you with a tracking number via email.
• Insurance: All shipments are insured. In case of damage, please contact us via email within 48 hours of receiving the product with photographic evidence, please also ensure a report is logged with the delivery driver.

Returns Policy

• Return Period: In the event of an item being received which is 'not as specified', you can return your purchase within 14 days of delivery.
• Condition of Items: Items must be returned unused and in their original packaging.
• Return Method: All returns must be notified in writing to hello@ttinstruments.com, the email should accompany the order number, date and reason for return and must be within 14 days of delivery.
• Restocking Fees: A restocking fee of up-to 20% is applicable for items returned for any reason other than 'not as specified'.
• Refund Method: Refunds are processed to the original method of payment within 5 business days of receiving the return.
• Exchanges: We do not offer exchanges. It will either be a replacement or a refund.
• Return Shipping Costs: Return shipping costs will be borne by the customer unless the item is 'not as specified', in this case we will arrange for the return by way of a prepaid shipping label.