1:4 and 2 x 1:2 RS-422 Fanout Buffer, Triax I/Os


$ 2,018.25


  • RS-422 Fanout Buffer
  • Clock/Data Fanout Buffer
  • High Speed Digital Communications Systems Testing
  • Satellite Telemetry/Ground Station System Integration


  • fmax > 75 MHz
  • 2.8 ns Typical Output Rise & Fall Times
  • 1 ns Typical Channel to Channel Skew
  • Floating 124 Ω Differential Inputs for RS-422
  • 4 Complementary 124 Ω RS-422 Outputs
  • Triax I/Os, Trompeter CBBJR79 or compatible
  • Switchable 1:4 Fanout or 2 x 1:2 Fanout Mode for simultaneous CLK/DATA distribution
  • Self-contained 1.3 x 2.9 x 6.0-in. unit
    includes ±8.5 V/1.8 A AC/DC Adapter


The PRL-414RSTR is a 1:4 fanout differential RS-422 line driver. It has two sets of floating 124 Ω differential inputs designed to accept RS-422 signals. The PRL-414RSTR high speed fanout line driver facilitates testing and integration of high speed digital communications circuits and distribution of satellite signals.

The PRL-414RSTR has two fanout modes, selectable by a toggle switch:

  • In the 1:4 mode (switch Up) D1 is connected to all four outputs Q1-Q4, and D2 is ignored. This mode is used for fanout of a single signal to four receivers.
  • In the 2 x 1:2 mode (switch Down) each of the two input signals is distributed to two outputs, with D1 connected to Q1-Q2, and D2 connected to Q3-Q4. This mode allows simultaneous distribution of Clock and Data signals to two receivers.

The four sets of differential outputs are 62 Ω back-terminated and designed for driving floating 124 Ω loads, normally the configuration used in RS-422 input circuits. The output swing is typically 1.40 V with a common mode voltage of 1.55 V. .

Because every output is independently buffered, unused outputs do not require termination, and outputs can even be shorted without affecting other outputs. These applications would not be possible with a passive splitter or powered distribution amplifier.

Multiple units of PRL-414RSTR can be cascaded for wider fanout, such as 1:16 or higher. The PRL-414RSTR can be combined with other PRL products and integrated into a rack-mount system using PRL's modular rackmount kit, PRL-MRK3-1.

All I/Os are Triax, using Trompeter CBBJR79 or equivalent, and will mate with any Trompeter 70-series Triax Cable Plug with 3 lugs, or compatible connector.

The PRL-414RSTR is supplied with a ±8.5 V/1.4 A AC/DC adapter and housed in a 1.3 x 2.9 x 6.0-in. extruded aluminum enclosure. Available accessories include voltage distribution modules and shielded twisted pair cables with Triax termination:

  • 88001140-36 Cable, Shielded Twisted Pair, 124 Ohm Triax to Triax, 36"
  • 88001140-48 Cable, Shielded Twisted Pair, 124 Ohm Triax to Triax, 48"

A related version with TTL/BNC inputs is also available, the PRL-414TRSBTR.


(0° C ≤ TA ≤ 35° C)*

Symbol Parameter Min Typ Max Unit Comments
RIN Differential Input Resistance   124   Ω  
RINC Common Mode Input Resistance   5k   Ω  
ROUT Differential Output Resistance   124   Ω  
VIN Input Voltage Range -7   +12 V Manufacturer’s specification;
not tested at PRL
VOL Output Low Level   0.85   V  
VOH Output High Level   2.25   V  
VOPP Voltage Output, peak-to-peak   1.40   V  
VCMO Output Common Mode Voltage1   1.55   V  
IDC1 DC Input Current   300
  mA F = 25 MHz
IDC2 DC Input Current   400
  mA F = 50 MHz
IDC3 DC Input Current   500
mA F = 75 MHz
VDC DC Input Voltage +7.5 +8.5 +12.0 V  
VAC1 AC/DC Adapter Input Voltage, 120 V 103 115 127 V  
VAC2 AC/DC Adapter Input Voltage, 220 V 206 220 254 V  
tPLH Propagation Delay to output ↑   20   ns  
tPHL Propagation Delay to output ↓   20   ns  
tr/tf Rise/Fall Times (10%-90%)2   2.8 3.5 ns  
tSKEW1 Differential Skew between Q and Q   200 350 ps  
tSKEW2 Skew between any 2 outputs   1000 1500 ps 1:4 Fanout Mode
tSKEW3 Skew between any 2 outputs   600 1000 ps 2 x 1:2 Fanout mode
fmax Max Clock Frequency3 75
  Size 1.3 x 2.9 x 6.0 in.  
  Weight 9 Oz w/o AC adapter
  Shipping Weight 4 lb w/AC adapter
(1) VCMO = (VOH-VOL)/2
(2) Rise and Fall times are measured using the PRL-860DTR, Low-Loss Triax Pickoff Tee. The through signals are driving a PRL-425TTR-C001, modified with a floating 124 Ω input, and the pickoff signals are driving 50 Ω scope inputs.
(3) fmax is measured using the PRL-177A Clock Generator driving the inputs via a PRL-Triax-SMA adapter and a PRL-425TTR-C001 as the receiver. The outputs of the PRL-425TTR-C001 are measured.