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serial network transmist delay buffer




Features / Benefits

  • Interface - RS-422/449
  • Optional: RS-530, V.35, RS-232 or X.21
  • 2.097 Mb buffer - bidirectional
  • Data Rates - Synchronous to 2.048Mbps
  • Timing - accepts external timing from each DCE device
  • 110/220VAC switch selectable


The RDS-SB is a device intended to provide a unidirectional 2.097 Mbit elastic data buffering (FIFO memory) function between two systems having nominally equivalent clocking rates. The two systems may be either running asynchronously, or may be traceable to a common timing source while one or both systems may possess a high degree of clock jitter.
The RDS-SB provides two DTE interfaces optionally configured as RS-449, X.21, EIA-530, or V.35. The maximum data transfer rate at each interface is 2.048 Mbps.
An option switch on the front panel allows the RDS-SB internal buffer memory to utilize a Differential Frequency Discriminator to prevent the FIFO memory from re-centering after an underrun or overflow until the frequency difference between the two external clocks is within a set range.
Data buffering is provided from the Receive Data (RD) input lead of Port A through the FIFO memory to the Send Data (SD) output lead of Port B. Data input on Port A is sampled on the clock edge occurring at the center of the data bit time period. Data output on Port B is latched on the clock edge occurring at the beginning of the data bit time period.

The 2.097 Mb First-In, First-out (FIFO) memory is used to buffer data in and out of the unit. Receive data may be simultaneously written into the FIFO while transmit data is read out. Internal counters track the FIFO level and are used to indicate underrun and overflow conditions, as well as indicate when the FIFO is half-full (centered) after initialization.
After a power-on cycle, or an underrun or overflow condition, the state of the FIFO is reset to an initial empty state, whereupon it will begin to accept input data at the Port A clock rate while inhibiting the output of data. Upon reaching a half-full (re-centered) state, the FIFO is enable to clock data out at the Port B clock rate.
A Differential Frequency Discriminator (DFD) may be invoked to conditionally hold off accepting received data and re-centering the FIFO after a power-on cycle, or an underrun or overflow condition occurs, until the frequency difference between the two port clocks falls within a set range of approximately 400 Hz. The purpose of this function is to prevent an out of range clocking source from repeatedly producing frequent underrun or overflow conditions.
When this function is invoked, and only after an underrun or overflow condition occurs, the FIFO memory is held in an initial state of empty if the DFD indicates that the absolute frequency differential is outside the range. If at any time within the sample window of the DFD (approx. 20mS), this differential should fall within the range, the FIFO will re-center normally and begin transferring data. (NOTE: It is possible in some cases that the average frequency differential will be outside the range, but may at times fall within the range due to clock jitter. This will be sufficient to trigger re-centering of the FIFO and transfer of data.)
The output of the DFD will be ignored as long as the FIFO continues to transfer data without an underrun or overflow condition occurring.
The RDS-SB is housed in a sturdy metal enclosure and operates on 110/220VAC.

The unit has a three year warranty and a 24 hour turnaround on warranty repairs.

Serial data buffer network diagram


Application Elastic data buffering (FIFO memory) function between two systems having nominally equivalent clocking rates
Buffer Size/Function 2.097 Mb First-In, First-out (FIFO) memory
Capacity Two(2) DCE devices, one for each port
Data Rates Up to 2.048Mbps
Data Channel Interfaces Available in V.35, RS-530, RS-422/449, RS-232 or X.21
Power Source 100-120 to 200-220VAC @10%, 50/60Hz, 0.16/0.08A, external 110/220 volt select switch, IEC Power Inlet, (2) 5mm Fuses
Environmental Operating Temperature....32º to 122º F (0º to 50º C)
Relative Humidity.............5 to 95%
Altitude............................0 to 10,000 feet
Dimensions Height ....... 1.75 inches (4.44 cm)
Width ........ 17.00 inches (43.18 cm)
Length ....... 9.00 inches
Weight 2 pounds (0.914Kg)
Warranty Three Years, Return to Factory
Ordering Information: Model: RDS-SB
Description: Selectable Transmit Buffer
Interfaces Available:
V.35, PT# 129010
RS-530, PT# 129011
RS-422/449, PT# 129012
X.21, PT# 129013
RS-232, PT# 129014
Included with each unit: 1) Operations Manual
2) U.S.A. Grounded Power Cord, Part # 713015
3) Optional Power Cords
A) United Kingdom, Part # 713016
B) Continental Europe, Part # 713017
C) Other: Specify Country on Purchase Order
 Surge Protection  Main power supply
Optional Accessories 1) Spare Data Center Fuses
A) 160ma Fuse, Qty (2) Part # 714000
B) 80ma Fuse, Qty (2) Part # 714001