Black Box SW177A Guia De Especificaciones

The 1284 standard is an IEEE

standard called “Signalling
Method for a Bidirectional
Parallel Peripheral Interface for
Personal Computers” used for
bidirectional parallel-printer-bus
support.

While standard parallel

interfaces can support speeds of
up to 150 kbps at distances of up
to 6 feet (1.8 m), IEEE 1284 parallel
interfaces can send your data
over six times faster and more
than five times the distance.

The standard specifies:

• All signals are twisted with

a signal line twisted to its
ground return.

• Each signal and ground

return must have a
characteristic impedance
of 62 ± 6 ohms over the
frequency band of 4 to
16 MHz.

• The wire-to-wire crosstalk

shall be no greater than 10%.

• The cable will have shielding

with a minimum of 85%
optical braid coverage
over foil.

Maximum Distance: 16.4 ft. (5 m)

Maximum Transfer Rate: 2 MB per

second (MBps)

Connectors: (3), (4), or (6) DB25 F

Indicators: LEDs: SW177A: None;

SW178A: (2) channel in use;
SW179A: (4) channel in use

Temperature Tolerance: Operating:

41 to 104°F (5 to 40°C)

Power: Interface-powered or

optional power supply

Size: SW177A: 1"H x 3.2"W x 3.6"D 

(2.5 x 8.1 x 9.1 cm); 

SW178A: 1"H x 7"W x 3.6"D 

(2.5 x 17.8 x 9.1 cm); 

SW179A: 1"H x 7.5"W x 3.6"D 

(2.5 x 19.1 x 9.1 cm)

Weight: SW177A: 0.3 lb. (0.1 kg);

SW178A: 0.4 lb. (0.2 kg); 
SW179A: 0.5 lb. (0.2 kg)

Technically Speaking

Specifications

Compact Bidirectional AutoSwitches

Reversible 1-to-2, 2-to-1.....................................SW177A
Dual Bus

2-to-2..................................................SW178A
4-to-2..................................................SW179A

To send data farther than 15 feet (4.6 m), order…
Optional Power Supply...........................................PS121-R2
You may also want to order…
Enhanced Parallel Port Cable, 6-ft. (1.8-m)

DB25 Male/DB25 Male ................................EQN200-0006
DB25 Male/DB25 Female ............................EQN201-0006
DB25 Male/Centronics 36 Male ................EQN202-0006

• The cable shield shall be

connected to the connector
back shell using a 360°
concentric method. A pigtail
connection is not
acceptable.

• Compliant cable assemblies

shall be marked: “IEEE Std
1284-1994 Compliant.”

The standard defines two

interface levels and specifies a
physical and electrical interface.

The Level I Interface is for

devices that need reverse-mode
capabilities but do not operate at
high speeds. The Level II interface
is for both bidirectional and high-
speed communications.

The 1284 standard also

defines connectors for use in
the parallel interface. The 25-pin
DB25 connector is defined as the
Type “A” connector. The Telco
36, 36-conductor, 0.085" centerline
Champ connector with bale locks
is defined as the Type “B”
connector. The Type “C”
connector is a 36-contact, 0.050"
centerline mini connector with
clip latches.

• You wait more than 30

minutes to get through to a
vendor’s tech support.

• The so-called “tech” can’t

help you or gives you the
wrong answer.

• You don’t have a purchase

order number and the tech
refuses to help you.

• It’s 9 p. m. and you need help,

but your vendor’s tech
support line is closed.

According to a survey by Data

Communications magazine, 90%
of network managers surveyed
say that getting the technical
support they need is extremely
important when choosing a

vendor. But even though network
managers pay anywhere from 10
to 20% of their overall purchase
price for a basic service and
support contract, the technical
support and service they receive
falls far short of their
expectations—and certainly isn’t
worth what they paid.

At Black Box, we guarantee

the best value and the best
support. You can even consult our
Technical Support Experts before
you buy if you need help selecting
just the right component for your
application.

Don’t waste time and

money—call Black Box today.

Why Buy From Black Box? Exceptional
Value. Exceptional Tech Support. Period.