CommSync II® Model 385

CommSync II is a fully-redundant modular time and frequency system combining dual GPS receivers, oscillators, and up to 13 output option modules in a single 3U chassis. The heart of the system is the GTF (GPS Time and Frequency) reference module, a hot-swappable, front panel plug-in module (with two slots available for redundancy). It is a self-contained module with Quartz Crystal (OCXO) or Rubidium Atomic oscillator options, as well as Civil, SAASM/M-Code MPE-S GB-GRAM, or SAASM/M-Code Force 22E MRU GPS receiver options. Dual Power Supplies and Reference Modules can provide redundancy with uninterrupted automatic switchover.



Utilized as a Primary Reference Source (PRS), the CommSync II provides either Standard Positioning Service (SPS) GPS or the very latest in GPS military technology – SAASM/M-Code Precision Positioning Service (PPS) GPS receivers (for authorized users only).

With GPS as the reference source, the CommSync II provides a frequency accuracy of 1E-12 and a time accuracy of < 50 ns Peak to UTC. Additional I/O slots can be utilized by configuring a slaved CommSync II with Distribution Time and Frequency (DTF) modules.

For Monitor and Control functions there is an RS-232 communications port on the front panel of the GTF/DTF module, a front panel keypad and display, as well as optional Gigabit Ethernet plug-in modules providing Telnet, SNMP, PTP v2 (1588-2008), and NTP. Zyfer™ Monitor (FEI-Zyfer’s remote access utility) provides complete remote control, including system status, setup, alarm logging and user management over a standard TCP/IP connection.

FEI-Zyfer products come with a standard 2 year factory warranty (parts & labor).


  • Full Redundancy: 
    Dual GPS Reference
    Dual Power Inputs
  • 13 I/O Module Slots
    100+ Option Modules
  • Dual GPS Receivers:
    Standard Civil C/A-Code
    and/or SAASM/M-Code MPE-S
    GB-GRAM or SAASM/M-Code
    Force 22E MRU Military
  • User Interface:
    Standard RS-232
    Optional Ethernet I/O
    (Telnet, SNMP)
    Keypad, LCD display
  • Remote Access Utility:
    Zyfer™ Monitor
  • Standard Outputs:
    1 PPS, 10 MHz
    (Front Panel)
  • Calibration:
    All units are calibrated with
    an in-house standard
    traceable to UTC


 24 Hour Average  Rubidium Oscillator  Quartz Oscillator
 Locked to GPS  < 1E-12  < 1E-12
 Holdover (b) first 24 hours  < 5E-11  < 1E-10


   Rubidium Oscillator  Quartz Oscillator
 Locked to GPS  < 50 ns Peak  < 50 ns Peak
 Holdover (b) first 24 hours  < 3 μs  < 7 μs


 Allan Deviation  Rubidium Oscillator  Quartz Oscillator
 1 sec  < 3E-11  < 1E-11
 10 sec  < 1E-11  < 1E-11
 100 sec  < 3E-12  < 1E-10


   Standard Output  Low Noise 5MHz
 1 Hz  < -90 dBc/Hz  < -105 dBc/Hz
 10 Hz  < -105 dBc/Hz  < -130 dBc/Hz
 100 Hz  < -125 dBc/Hz  < -150 dBc/Hz
 1 kHz  < -135 dBc/Hz  < -158 dBc/Hz
 Standard GPS Receiver – Civil C/A-Code:
 Type:  8 to 12 channel, independent tracking
 Frequency:  1575.42 MHz (L1)
 Code:  C/A
 Acquisition Time:  Warm Start: < 2 minutes, Cold Start: < 20 minutes.
 SAASM/M-Code GPS Receiver – Military P(Y)-Code:
 Type:  12 channel, independent tracking
 Frequency:  1575.42 MHz and 1227.60 MHz (L1 & L2)
 Code:  C/A and P(Y)
 Acquisition Time:  Warm Start: < 2 minutes, Hot/Cold Start: Dependent on  Initialization Device (f).
 Keyload Interface:  DS-102
 FORCE 22E MRU SAASM/M-Code GPS Receiver – Military C/A and P(Y)-Code: (e)
 Type:  24 channel, simultaneous tracking of L1, L2 and C/A codes
 Frequency:  1575.42 MHz and 1227.60 MHz (L1 & L2)
 Code:  C/A and P(Y)
 Acquisition Time: (c)  Warm Start: < 2 minutes
Hot/Cold Start: Dependent on Initialization Device
 Keyload Interface:  DS-102
 with Standard GPS Receiver  with SAASM/M-Code GPS Receiver (e)
 1 PPS,
50 Ω, TTL level, SMA, Ext. Sync Input
 1 PPS, 50 Ω,
TTL level, SMA, External Sync Input
 RS-232 I/O connector  RS-232 I/O connector
 10 MHz, 50 Ω, TTL level, SMA connector  10 MHz, 50 Ω, TTL level, SMA connector
 1 PPS, 50 Ω,
TTL level, SMA connector
 1 PPS, 50 Ω,
TTL level, SMA connector
 Keyload Interface – DS-102
 Hot Start connector
Single or Dual Power Supplies, AC or DC or a combination of the two
 AC Input (115/230 VAC)  90 to 264 VAC, 150 Watts maximum, 47-63 Hz
 DC Input (24 VDC)  18 to 36 VDC, 150 Watts maximum
 DC Input (48 VDC)  36 to 76 VDC, 150 Watts maximum
 DC Input (12 VDC)  11.5 to 18 VDC, 150 Watts maximum
 DC Input (28 VDC aircraft bus)  22 to 29 VDC, 150 Watts maximum
 Height:  134 mm (5.25″) (3U)
 Width:  448 mm (17.65) (19″ EIA Rack)
 Depth:  381 mm (15.0″) including connectors
 Weight:  25 lbs. (max.)
 Operating Temperature:  0° C to 50° C
 Rate of Change:  10° C/Hour
 Storage Temperature:  -40° C to +85° C
 Relative Humidity:  5 % to 95 %, non-condensing
 Altitude, Operating:  –60 m to 4000 m
 Altitude, Storage:  60 m to 9000 m
FCC Code of Federal Regulations 47CFR Part 15, Subpart B, Class B

(a) After 24 hours of GPS locked operation, fixed antenna location, antenna delays entered.
(b) After 48 hours of continuous operation.
(c) 2σ (95.5 % probability).
(d) Detailed specifications for various output modules: See “Option Module User’s Manual 385-8003”.
(e) U.S. Government policy restricts the sale of Precise Positioning Service (PPS) equipment to those
authorized by the U.S. Department of Defense. Non-U.S. authorized users must purchase PPS equipment
through the Foreign Military Sales (FMS) process.
(f) Dependent on the accuracy of initialization parameters from PLGR or DAGR handheld SAASM/M-Code GB-GRAM receivers, or other initialization devices.

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