The Marconi IFR Aeroflex 2851S Digital Transmission Analyzer is a portable instrument for installation, maintenance, and troubleshooting of digital transmission systems. It combines data and PCM rate testing with error performance analysis across multiple framing standards and bit rates, supporting both European and North American digital hierarchies. The 2851S performs synchronized and asynchronous data interface testing, signal analysis, and propagation delay measurement in field and laboratory settings.
Technical Specifications
Data Rate Support
• PCM and digital transmission: 704 kbit/s, 1544 kbit/s, 2048 kbit/s, 3152 kbit/s, 6312 kbit/s, 8448 kbit/s
• Data interfaces: 50 bit/s to 2.5 Mbit/s in 1 bit/s steps
• Bit rate accuracy (transmitter): 704 kbit/s ±50 ppm; 1544 kbit/s ±130 ppm; 2048 kbit/s ±50 ppm; 3152 kbit/s ±30 ppm; 6312 kbit/s ±33 ppm; 8448 kbit/s ±30 ppm
Framing Support
• T1 variants: T1, T1 no signaling, T1ESF, T1ESF no signaling, T1DM, DDS Data Mux
• G.704 modes: standard, no multiframe, with CRC, with CRC no multiframe, 32 frame multiframe
• DS1C: mode 1 synchronous, mode 2 asynchronous
• DS2: 96 channels synchronous, asynchronous, 2048 kbit/s interworking to G.704
• 10-channel systems at 704 kbit/s
Error Analysis
• Error rate measurement: 1×10⁻³ to 1×10⁻⁷
• Pseudo-random burst: user-selectable lengths (8, 16, 32, 64, 128, 256 errors)
• Errored blocks: 1–999 per 1,000 or 60,000 blocks
• Programmable thresholds for Severely Errored Seconds, Degraded Minutes, and Errored Seconds
– Key Features
• RS-232, X.21, RS-449 (V.36), and V.35 data interfaces; codirectional and contradirectional modes (2850B and 2851)
• DTMF and Channel Associated Signaling (CAS) capability
• Structured data testing: X.50, 6+2, and reiterated systems
• Frequency deviation, frequency, and level measurement
• Propagation delay measurement
• EUROCOM D/1 optional interface for European military networks
– Typical Applications
• Digital transmission system installation and acceptance testing
• Network maintenance and performance validation
• Transmission line troubleshooting and error diagnostics
• PCM and data interface characterization
– Compatibility & Integration
Supports synchronous and asynchronous operation modes with standard and user-programmable data rates. Accommodates both European (G.704) and North American (T1/DS) digital hierarchies.
