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MODEL SS1 - 2 x 1 SCSI Switch for Rack Mount or Tabletop

SCSI Switch Model SS1


  • Switch between Primary and Backup devices during system maintenance.
  • Access a single device or group of devices from more than one host.
  • Switch between two devices or groups of devices with the same SCSI address.
  • Access for more than the 15 SCSI devices normally available to a Wide SCSI Port.
  • Does not consume a SCSI address

The SS1 SCSI Bus Switch allows two hosts to share peripherals or one host to access either of two sets of peripherals. Each port may be SE, HVD or LVD. Switching from one port to the other may be accomplished: a. locally with the front panel switch, b. remotely with a momentary dry contact closure, or c. remotely via the RS-232 port. A software template for the RS-232 port is included in the User Manual. In all cases switching does not occur until "bus free."

In mode One, Port 1 is connected to the Common Port. In mode Two, Port 2 is connected to the Common Port. A front panel LED displays the selected port. Each port supports a full SCSI cable length and provides term power and termination, which may be disabled. The SS1 does not consume a SCSI device ID, is transparent to both initiator and target, and does not slow data throughput. Devices on the LVD ports run at SCSI throughput up to 160 Mbytes/sec, HVD and SE ports run at up to 40 Mbytes/sec. An amber LED for each port indicates bus activity and a green LED indicates that each port is powered. See Rear View Photo. For a printer friendly version of this information, please see the PDF version of this data sheet.

A front panel 7-segment LED display shows the active port.

Switch diagram

PDF version of this data sheet.

SCSI Interface:
Order LVD/MSE, HVD or SE for each port
LVD supports Ultra 160
HVD or SE supports Ultra
Cable Length & Data Throughput:
LVD - up to 160 Mbytes/sec
25 m (82 ft) point-to-point
12 m (40 ft) with more than 2 IDs
SE - up to 40 Mbytes/sec
6 m (20 ft) SLOW SCSI
3 m (10 ft) FAST SCSI
1.5 m (5 ft) Ultra SCSI
HVD - up to 40 Mbytes/sec
25 m (82 ft)
Serial Interface:
Mode: 8 bits, 1 stop bit, no parity
Baud Rate: 9600 baud
Max Cable Length: 50 feet
The Paralan SCSI Switch is designed to operate in an office environment with limited capacity for heating and air conditioning.

Temperature Range:
Operating: 0 to +50 C
Storage: -25 to +75C
Humidity Range:
Operating: 5 to 90% RH
Storage: 5 to 95% non-condensing
All Metal
Wide SCSI: 68-pin High-Density, female Alt 3, P Connector
Narrow SCSI: 50-pin centronics type, female Alt 2, A connector
Maximum Power Requirements: 40 Watts
Line Voltage: 90 to 264 VAC,
47 to 63 Hz Auto-Ranging
FCC Class B, CE
16.75 x 10.0 x 1.72 (425.5 x 254 x 43.7 mm)
Vertical Rack Space 1U (1.75 inches, 44.5 mm)
Rear Panel PDF Drawing with Full Dimensions
11 lbs (5 kg)
22 lbs (10 kg) shipping

Rear View Dimensions of SCSI Switch Model SS1

The Model SSI SCSI Switch allows three independent SCSI Buses to be connected in several configurations as delineated in the table below:

LVD/MSE, HVD or SE (Wide) HVD LVD/MSE, HVD or SE (Wide)
LVD/MSE, HVD or SE (Wide) SE (Wide) LVD/MSE, HVD or SE (Wide)
SE (Narrow) SE (Narrow) SE (Narrow)

ORDERING GUIDE FOR SCSI SWITCH, Standard Configurations:

SCSI 2 X 1 Switch For Tabletop or Rack
Model No.: SS1
  X X X T or R
Select one letter from each column:  
High Voltage Differential (HVD) Wide port
  H H H
Multimode LVD (LVD/MSE) Wide port
  L L L
Single-ended Wide (68-pin HD connector)
  S S S
Tabletop Enclosure with Rubber Feet  -------------
Adapters for Rack Mounting the Switch - 1 Pair  ------------- --------------

Custom switch inquiries for OEM quantities are welcome.
Example 1: Model No. SS1-LHL-T - Tabletop Model SS1 with LVD/MSE at both switched ports and HVD at the Common port
Example 2: Model No. SS1-SLH-R - Rack Mount Model SS1 with LVD/MSE at the Common port, SE Wide at Port 1 and HVD at Port 2


  • The SS1 comes assembled and wired with the selected Ports installed.
  • A six foot (1.84 m) North American grounded cordset (NEMA 5-15, rated 250 VAC) is included in shipments to destinations in North America and Japan. Other destinations receive no cordset.
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