Chapter 9. Larus Synchronization Timing Systems

The Larus Model STS 5400 and Model STS 5800 Synchronization Timing Systems are designed to solve most of the timing problems encountered in long distance, local telephone company, and private digital networks. The STS 5400 provides DS1, composite clock, E1 and 2.048 MHz square wave outputs for telephone company BITS clock applications. The 5400 is intended for medium to large applications. The 5800 system is utilized to provide accurate and reliable synchronization in remote locations or in customer premises applications. The STS 5800 provides ten 64/8 Kb/S Composite Clock outputs, ten 1.544 Mb/S or EFS outputs and four RS-422 Transistor-Transistor logic (TTL) 1.55 MHz outputs.

STS 5400 System

The STS 5400 provides extensive monitoring and management capabilities, and a Stratum 2 clock option. These features are desirable for the larger synchronization networks. The STS 5400 is available in two versions, Stratum 2 and Stratum 3E Enhanced. The Stratum 3E Enhanced system uses DS1 bridging input cards and track and hold cards. Stratum 2 arrangements are equipped with double width input track and hold cards. The input cards convert DS1 inputs into reference timing for the track and hold circuits. The track and hold cards provide the essential features of jitter smoothing and holdover clock on input reference failure. The output cards provide DS1, E1 (2.048 MHz square wave) or 64/8 kb/S composite clock outputs for driving D type channel banks, DACS, transmuxes, PBXs or other network transmission and switching equipment.

The STS 5400 circuit card family comprises the following modules:

• 5401 DS1 Bridging Input
• 5402 Stratum 3E Enhanced Track & Hold
• 5403 Stratum 2 Track & Hold
• 5404 Performance Monitor
• 5405 Information Management
• 5406 Alarm Interface
• 5407 DS1 Output Driver
• 5408 Composite Clock Output Driver
• 5409 E1 Output Driver/2.048 MHz Square Wave Output Driver
• 5410 GPS Track and Hold, Stratum 2 Holdover
• 5411 10 MHz Signal Tracking
• 5412 GPS Track and Hold, Stratum 3E Enhanced Holdover
• 5413 RS-422 Square Wave Output Driver

The 5401, used in Stratum 3E Enhanced arrangements only, bridges existing DS1 circuits to extract data and timing information for use by the 5402 Track and Hold card.

The 5402 (Stratum 3E Enhanced) and 5403 (Stratum 2) Track & Hold cards take either direct inputs (5403) or the outputs from the bridging input cards (5402), and process the information to derive a stable 1.544 Mb/S timing signal for the output cards. A GPS receiver and Stratum 2 clock are integrated into the 5410 card.

The 5404 Performance Monitor Card measures DS1 input performance. The 5405 Information Management Card provides local and remote status reporting through RS232 ports. Alarm status information from other cards is gathered by the 5406 Alarm Interface Card. The combination of the 5404 and the 5405 cards provide integrated performance monitoring, service threshold alarms, local and remote interface using either a menu driven input, TL1 output system, or a TL1 input and output system. A rack mounted X.25 PAD Model Number 25500 is also available for the remote interface.

Output cards receive timing signals from Track and Hold cards and provide multiple outputs. The 5407 provides ten DS1 framed ones outputs. The 5408 provides ten 64/8 kb/S Composite Clock outputs. The 5409 provides either E1 framed ones, or 2.048 square wave outputs to drive channel banks or other equipment.

The 5411 Signal Tracking card accepts two 1.544 MHz DS1 reference signals, extracts timing, and provides a smoothed and essentially jitter free tracking signal to the output cards. The 5411 requires a high stability external timing source such as a GPS receiver or a cesium clock.

The master shelf houses the track and hold clock modules (Stratum 3E, 2 or GPS Receiver), the system monitoring and reporting cards, as well as ten (10) output cards. The shelf provides a complete 100 output timing system. Extension shelves may be added for 100 outputs per extension, up to three extensions for 400 total outputs in one system.

An output switch shelf may be added for older equipment that does not have duplicate synchronization inputs. The switch shelf may be provisioned with only those relay matrix cards necessary in order to reduce cost and maintain reliability.

STS 5800 System

STS 5800 Synchronization Timing System provides an accurate and reliable way to synchronize communications NEs in a remote location, or in a customer premises application. By synchronizing all the equipment, especially switching and multiplexing NEs, across a network, a user can maximize the utilization of network equipment and minimize network transmission errors.

The STS 5800 is a fully modular self-contained system, designed to operate over an extended temperature range, from -40 °C to +75 °C. The STS 5800 is packaged in NEBS compatible 19/23 inch mounting enclosure, which contains all features and options as ordered per the List number. There are no user replaceable assemblies. The entire unit uses only quick connect/disconnect connectors for all interfaces.

The STS 5800 List 0 system contains an input signal processing block for clock distribution. List 1 through 5 one track and hold processing sub unit. Lists 3 and 5 contain a GPS receiver. List 3 through 5 are provided with Information Management and Performance Monitoring. All List options provide ten DS1 outputs, ten Composite Clock outputs and four RS422 outputs. Details of the STS 5800 list options are as follows:

The STS 5800 provides a fully redundant wander and jitter-free source of framed ones, composite clock and square waves synchronized to a suitable framed DS1 reference or GPS atomic time reference. Jitter and wander attenuation is a standard function of Track and Hold.

For the Stratum 1 system, the input tracking reference is derived from a set of cesium beam atomic clocks a board orbiting GPS satellites whose signals are received by onboard GPS receivers. Stratum 3E systems use external signals as tracking references.

The STS 5800 is non-revertive. If the primary DS1 reference fails and the Track and Hold Function switches to use the secondary DS1 input, the Track and Hold Function will not switch back to use the primary DS1 input unless the secondary input fails.