Condition: Used Refer to images for cosmetic condition and the description below for what is included.Note we have multiple units so actual product may differ a little. Included in the sale: TM-4M Time & Frequency Reference System Accessories are as pictured

The Spectrum Instruments Intelligent Reference TM-4M is a portable, rechargeable, multiple-output, GPS-disciplined time and frequency reference system. Designed for field and laboratory use, the TM-4M builds on the core TM-4 platform and adds an internal rechargeable battery, making it fully self-contained for portable deployments. It is used across wireless, telecom, synchronisation, data acquisition, calibration, and scientific applications.

The TM-4M uses a GPS-disciplined ovenised crystal oscillator (OCXO) as its primary frequency reference. Spectrum's exclusive FastStart™ technology brings the unit to high accuracy within minutes of power-up, far faster than conventional GPS-disciplined oscillators. The Intelligent Holdover™ function maintains near-Rubidium stability during periods of GPS unavailability.

Six BNC connectors on the front panel are user-assignable to output any of the available signals. Two multiplexer outputs provide selectable TTL frequency outputs slaved to the primary reference: 1 kHz, 10 kHz, 100 kHz, 1 MHz, 5 MHz, and 10 MHz. An RS-232 control port allows full control and monitoring by a host computer. A Time Port delivers ASCII serial time messages in Spectrum, NMEA, or optional NTP formats.

Key Features:
• GPS-disciplined ovenised oscillator (OCXO) with very low phase noise
• FastStart™ technology — high accuracy achieved within minutes of start-up
• Intelligent Holdover™ — near-Rubidium stability without GPS signal
• Internal rechargeable battery for portable field operation
• Six user-assignable BNC output connectors
• Event Time-Tag (ETT) function with 100 ns resolution
• RS-232 control interface for host computer control
• ASCII serial time message output (Spectrum, NMEA, or NTP)
• Optional synthesised timing pulse output coherent with 10 MHz clock

Typical Applications:
Frequency reference: Wireless networks, telecom infrastructure
Synchronisation: Data acquisition systems, test and measurement equipment
Calibration: Laboratory standards, signal generator and spectrum analyser locking
Scientific: Astronomy, research, and precision timing

Specifications (TM-4 platform — refer to TM-4M Addendum for variant-specific details):
Primary Output Frequency: 10 MHz
Oscillator Type: GPS-disciplined OCXO (standard); VCXO and other options available
Frequency Accuracy (locked): Better than 1 part in 10^12 (GPS-disciplined)
Frequency Accuracy (fine tuning entry): Better than 1 in 10^9
Multiplexer Output Frequencies: 1 kHz, 10 kHz, 100 kHz, 1 MHz, 5 MHz, 10 MHz (TTL)
Event Time-Tag Resolution: 100 ns
Serial Interface: RS-232, default 9600 bps (configurable)
GPS Receiver Frequency: L1, 1575.42 MHz
Output Connectors: 6 x BNC (user-assignable)
Control/Time Ports: 2 x DB9 (RS-232)
Power: Internal rechargeable battery with AC charging
Form Factor: Compact portable chassis with carry case

TM-4M product cut sheet — features and applications overview: Download PDF

TM-4M Addendum — TM-4M specific features and differences from standard TM-4: Download PDF

Intelligent Reference TM-4 User Manual — full operating manual applicable to TM-4M platform: Download PDF

Intelligent Reference TM-4 and TM-4/OEM product datasheet — specifications and features: Download PDF