Couplers

Data Bus
Couplers

A Data Bus Coupler is a small interface module used to connect each Remote Terminal or Node to the main data bus while protecting the bus from faults. It includes Bus-In and Bus-Out lines for the main bus and one or more stub ports that connect to equipment. Each stub uses a coupling transformer and two isolation resistors, which help maintain the correct bus impedance, reduce signal reflections, and provide electrical isolation. This design ensures that if a stub or terminal becomes shorted or fails, the main bus continues to work normally without interruption.

Couplers with connectors attached directly into the housing are called connectorized Data Bus Couplers, offering simpler installation and better reliability. Overall, VIBRAN couplers ensures clean signal transmission, proper impedance matching, and fault protection for the entire data bus system.

Box · BJ77 Box · D-Sub Inline

Box Couplers
BJ77 Connector

Flagship connectorized box coupler with bayonet type triax connectors. Encapsulated construction with coupling transformer complied to MIL-T-21038 and fault-protection resistors complied to MIL-R-39007. Available as 2-stub (VT 1002) and 4-stub (VT 1004) variants with and without internal terminations.

NOTE · The cost between 1 & 2 and 3 & 4 stub couplers is negligible, so Vibran does not manufacture 1 & 3 stub couplers.

BJ77 Box Couplers — VT 1002 and VT 1004
§ BJ77Specifications · designed for MIL-T-21038
Transformer turns ratio
1 : 1.41 (±3%) MIL-T-21038
Common-mode rejection (CMR)
> 55 dB @ 1 MHz with 10 V RMS MIL-T-21038
Open-circuit impedance (75 kHz – 1 MHz)
|Z| > 10 kΩ min @ 25 °C MIL-T-21038
Waveform integrity (droop)
20% max · 250 kHz square, 90 ns ±5% rise/fall MIL-T-21038
Overshoot & ringing
±1.0 V peak · 250 kHz square, 100 ns max rise/fall MIL-T-21038
Isolation resistors (in series)
59 Ω / 1 W (±1%)
Insulation resistance — winding to winding
Ri > 1 000 MΩ @ 250 VDC
Insulation resistance — bus / stub
> 1 000 MΩ @ 250 VDC
Insulation resistance — inner contacts / shield
> 1 000 MΩ @ 500 VDC
Primary DC resistance
< 2.7 Ω MIL-T-21038
Secondary DC resistance
< 2 Ω MIL-T-21038
Primary parallel inductance
> 40 mH
Primary shunt capacitance
< 35 pF
Inter-winding capacitance
< 45 pF
Primary leakage inductance
< 6 μH
Shield continuity
< 100 mΩ
Stub voltage
1 Vpp — 14 Vpp (transformer-coupled)
Termination
78 Ω ±2%, 1 W (optional)
Connector type
BJ77 · jack type / socket contact, bayonet-coupled triax
Operating temperature
−50 °C to +125 °C
Storage temperature
−50 °C to +125 °C
Body case
Aluminium 6061 with Black Anodization
Coupler module
Encapsulated · transformer to MIL-T-21038 + fault-protection resistors to MIL-R-39007
VT 1002 · 2-Stub Data Bus Coupler
VT 1002< 110 g
2-stub
Two-stub connectorized Data Bus Coupler for compact installations with up to two terminals.
VT 1004 · 4-Stub Data Bus Coupler
VT 1004< 180 g
4-stub
Four-stub connectorized Data Bus Coupler for installations requiring up to four terminal connections.
Box · BJ77 Box · D-Sub Inline

Box Couplers
D-Sub Connector

D-Sub connector based box couplers are used primarily in testing labs, test rigs, and simulators where cost is a significant concern. Substantially lower cost than BJ77 and Inline while meeting the same MIL-T-21038 performance. It is available in standard 4 stub configuration by default.

D-Sub Box Coupler — 4-stub Data Bus Coupler
§ D-SUBSpecifications · designed for MIL-T-21038
Transformer turns ratio
1 : 1.41 (±3%) MIL-T-21038
Common-mode rejection (CMR)
> 55 dB @ 1 MHz with 10 V RMS MIL-T-21038
Open-circuit impedance (75 kHz – 1 MHz)
|Z| > 10 kΩ min @ 25 °C MIL-T-21038
Waveform integrity (droop)
20% max · 250 kHz square, 90 ns ±5% rise/fall MIL-T-21038
Overshoot & ringing
±1.0 V peak · 250 kHz square, 100 ns max rise/fall MIL-T-21038
Isolation resistors (in series)
59 Ω / 1 W (±1%)
Insulation resistance — winding to winding
Ri > 1 000 MΩ @ 250 VDC
Insulation resistance — bus / stub
> 1 000 MΩ @ 250 VDC
Insulation resistance — inner contacts / shield
> 1 000 MΩ @ 500 VDC
Primary DC resistance
< 2.7 Ω MIL-T-21038
Secondary DC resistance
< 2 Ω MIL-T-21038
Primary parallel inductance
> 40 mH
Primary shunt capacitance
< 35 pF
Inter-winding capacitance
< 45 pF
Primary leakage inductance
< 6 μH
Shield continuity
< 100 mΩ
Stub voltage
1 Vpp — 14 Vpp (transformer-coupled)
Termination
78 Ω ±2%, 1 W (optional)
Connector type
15-pin D-Sub connector on side
Operating temperature
−50 °C to +125 °C
Storage temperature
−50 °C to +125 °C
Body case
Aluminium 6061 with Black Anodization
Coupler module
Encapsulated · transformer to MIL-T-21038 + fault-protection resistors to MIL-R-39007
D-Sub Box Coupler — 4-stub
D-Sub
4-stub
Four-stub 15-pin D-Sub Data Bus Coupler for test labs, test rigs, and simulators.
Box · BJ77 Box · D-Sub Inline

Inline Couplers
Custom — contact us

Manufactured to custom cable lengths and connector types per project requirement. Supports 1 to 4 stubs per coupler with PL75-47 / DK series or customer-specified connector.

Inline Data Bus Coupler — custom cable length
§ INLINESpecifications · designed for MIL-T-21038
Transformer turns ratio
1 : 1.41 (±3%) MIL-T-21038
Common-mode rejection (CMR)
> 55 dB @ 1 MHz with 10 V RMS MIL-T-21038
Open-circuit impedance (75 kHz – 1 MHz)
|Z| > 10 kΩ min @ 25 °C MIL-T-21038
Waveform integrity (droop)
20% max · 250 kHz square, 90 ns ±5% rise/fall MIL-T-21038
Overshoot & ringing
±1.0 V peak · 250 kHz square, 100 ns max rise/fall MIL-T-21038
Isolation resistors (in series)
59 Ω (±1%)
Insulation resistance — winding to winding
Ri > 1 000 MΩ @ 250 VDC
Insulation resistance — bus / stub
> 1 000 MΩ @ 250 VDC
Insulation resistance — inner contacts / shield
> 1 000 MΩ @ 500 VDC
Primary DC resistance
< 2.7 Ω MIL-T-21038
Secondary DC resistance
< 2 Ω MIL-T-21038
Primary parallel inductance
> 40 mH
Primary shunt capacitance
< 35 pF
Inter-winding capacitance
< 45 pF
Primary leakage inductance
< 6 μH
Shield continuity
< 100 mΩ
Stub voltage
1 Vpp — 14 Vpp (transformer-coupled)
Termination
78 Ω ±2%, 1 W (optional)
Connector type
PL75-47 / DK series / as per requirement
Cable type
10614-9 / equivalent / as per requirement
Cable length
As per requirement
Number of stubs
1 to 4 stubs
Operating temperature
−50 °C to +125 °C
Storage temperature
−50 °C to +155 °C
Coupler module
Encapsulated · transformer to MIL-T-21038 + fault-protection resistors to MIL-R-39007
Enquiries

Request a
quotation.

info@vibran-tek.com +91 8904 764 795