Digital Multiplexing Equipment PDF

CHAPTER XIV =========== 1. PRINCIPLE OF DIGITAL MULTIPLEXER ================================ 1. The existing digital multiplexing equipment are based on 2048 Kbps SDH -- (STM 1, STM 4, STM -- 16 or higher) 10 Mbps, 100 Mbps, 1 Gbps (Ethernet) based hierarchy. In future,...

CHAPTER XIV =========== 1. PRINCIPLE OF DIGITAL MULTIPLEXER ================================ 1. The existing digital multiplexing equipment are based on 2048 Kbps SDH -- (STM 1, STM 4, STM -- 16 or higher) 10 Mbps, 100 Mbps, 1 Gbps (Ethernet) based hierarchy. In future, it has been decided that all new work shall be based on IP-MPLS technology. 2. MEDIA OF TRANSMISSION ===================== - Symmetric cable pairs / HDSL modems - Star quad cable in 25 KV AC electrified areas - Optical fibre - Radio based communication 3. Primary multiplexing equipment ============================== a. This equipment shall multiplex 30 analogue and/or data channel to 2048 Kbps ITU compatible digital stream on transmit side and on receive side, it shall demultiplex ITU compatible 2048 Kbps digital stream to 30 analogue voice /data channels. b. Following type of primary multiplexers are in use: i. TERMINAL MUX ============ PRIMARY DROP/INSERT MUX ======================= DROP/INSERT MUX WITH CONFERENCE FACILITY ======================================== TYPE OF INTERFACE CARDS FOR THE PRIMARY MULTIPLEXER =================================================== - 2W speech card with E&M Signalling - 4W speech card with E&M signalling - Exchange end interface cards - Subscriber side interface cards - Hotline interface cards - Digital Subscriber Line Interface Card - Network Termination Unit/ Remote Data Unit - E1 Branching Interface - Data interface cards of various types like iv. G703 (64 Kbps Data Interface) v. NX64 Kbps data interface cards etc. 2. All digital multiplexing equipment shall be as per approved specification of RDSO. 3. CHARACTERISTICS OF INTERFACE ============================ a. BIT RATE 2048 Kbit/s ± 50 PPM b. Code HDB3 OUTPUT PORT: ============ a. Pulse shape Rectangular as per ITU T G.703 b. Pulse peak voltage 2.37V/75 ohm or 3.0v/120 ohm c. Normal pulse width 244 ns INPUT PORT: =========== a. Permissible attenuation F law 0 6 db at 1024 Khz b. RETURN LOSS REQUIREMENT OF SYSTEM PERFORMANCE ================================= i. The overall system performance with the proposed transmission media shall be so designed and ensured that it meets ITU T parameters. The system availability shall be at least 99.5%. ii. The characteristic of complete circuit shall be measured on the basis of audio frequency 4W/2W interface in respect of characteristics and parameters defined in ITU T G.712. iii. The measurement of performance parameters made during the life cycle of the equipment shall be within acceptable limits. 5. SYNCHRONIZATION =============== FRAME STRUCTURE 2048 Kbps TRIBUTARY =================================== FAULT CONDITION AND CONSEQUENT ACTION ===================================== Primary PCM Multiplexer Equipment ================================= a. Power supply failed. b. Loss of incoming signal at 64 Kbps input port c. Loss of incoming signals at 2048 kbps d. Loss of frame alignment e. Loss of multiframe alignment f. Excessive error ratio alarm in framing pattern for 1 in 10E 3 g. Remote failure h. AIS alarm i. Loss of transmit clock 8. Digital Cross Connect ===================== INSTALLATION ============ i. **SIZES OF ROOM** ii. SPACING ======= a. The spacing between ceiling and cable carrier from the rack may be (min) 30 CM. The cable carrier itself may be mounted 30 CM minimum above the rack. b. There must be a space of 2 meters (min) between two rows of double sided rack. c. The space between the equipment rack and wall/other racks should be minimum 2 meters. iii. It should be ensured that the room where the equipment is installed is well ventilated and illuminated and is at least 3 meters away from major sources of electromagnetic radiation such as photocopiers and facsimile machines. iv. The rack on which the equipment is to be mounted shall be on standards 19" rack. Minimum 2u spacing should be provided in between two equipment. The racks shall be provided with suitable covers on all sides to protect entry of rodents, etc. v. All connections from the equipment to be terminated on the suitable MDF mounted on the rack. All cables may be carried above the wayside on cable carriers separated from the ceiling. The cable carrier may be of 15 cm to 30 cm in width. vi. EARTHING ======== POWER SUPPLY ============ MAINTENANCE =========== i. **General Precaution and Instructions** ii. Electronic circuits on the multiplexer are easily damaged by electrostatic discharge. Hence, the following precautions are to be followed: - Always wear a proper anti static strap/ wristband. - Before handling any electronic components, touch the grounded metal surface to discharge static from your body. It is recommended to use antistatic flooring along the equipment on all the sides. - Avoid touching the components on the PCB. - Follow any other safety instructions provided by the manufacturer. iii. Some of the cards cannot be inserted with power supply ON. Proper precaution may be followed for removing or inserting such cards. iv. The PCBs should be transported to the repair center after electro statically sealing the card and as per the procedure specified by the supplier. v. Maintenance schedule for multiplexing equipment. The measurements may be carried out in line with relevant ITU T standards being updated from time to time (for e.g., ITU T G.823, 824, 825, etc.) +-----------------------+-----------------------+-----------------------+ | - | | | +=======================+=======================+=======================+ | - | | | +-----------------------+-----------------------+-----------------------+ | - | | | +-----------------------+-----------------------+-----------------------+ | all 2W/4W channels of | | | | primary MUX | | | | | | | | - Idle channel | | | | noise on all | | | | channels on | | | +-----------------------+-----------------------+-----------------------+ | - | | | +-----------------------+-----------------------+-----------------------+ | | | | +-----------------------+-----------------------+-----------------------+ | - | | | +-----------------------+-----------------------+-----------------------+ +-----------------------+-----------------------+-----------------------+ | - |.... | Yearly | +=======================+=======================+=======================+ | | | | +-----------------------+-----------------------+-----------------------+ | | | | +-----------------------+-----------------------+-----------------------+ | - |.... | Yearly | +-----------------------+-----------------------+-----------------------+ | - |.... | Yearly | +-----------------------+-----------------------+-----------------------+ | | | | +-----------------------+-----------------------+-----------------------+ | | | | +-----------------------+-----------------------+-----------------------+ FAILURES ======== TEST INSTRUMENT =============== a. Equipment to be provided at centralized location - PCM test set with facility for A to A and A to D, D to A, D to D testing. - BER test set with jitter measurement - Data tester - The insulation resistance measuring set - Cable fault locator - Earth resistance measuring set b. Equipment to be provided with each of the maintenance gang -- - PCM MUX tester with facility to test at least up to 8 Mbps with framed and unframed signal - Digital multi meter - Portable PCM test set - Signalling test set INSPECTION, RECORD AND REPORT ============================= a. Three monthly and six monthly test shall be carried out by the JE/SSE of the section and he shall maintain all the records. b. Yearly schedule of maintenance shall be carried out by the JE/SSE In charge. The critical yearly schedule/tests/adjustments shall be carried out under the supervision of ADSTE/DSTE. The records of the tests and maintenance schedule shall be maintained in the relevant pro forma. c. ADSTE/DSTE/Sr.DSTE during their annual inspection shall check the record of tests and failures and availability of proper instruments and details of testing. 4. SDH EQUIPMENTS ============== -- -- -- -- 11. SYSTEMS CHARACTERISTICS & PERFORMANCE ===================================== c. The TEC Generic specification as per requirement is adopted. The system shall be capable of interfacing with optic fibre cable as per latest RDSO specification with latest amendments. d. Configuration ============= - Point to point topology - Bus topology - Mesh topology - Ring topology Multiplexing ============ Tributaries =========== - E1 (2Mbps) - Tributary STMs - 10/100/1000 Mbps Ethernet systems Alarms & Indications ==================== Installations ============= Protection switching ==================== MAINTENANCE =========== i. The SSE/JE of the section should maintain close liaison with the Engineers/Managers of RailTel Corporation of India (RCIL) in ensuring proper maintenance of the SDH equipment wherever the maintenance is being carried out by RCIL.Joint testing of protection channels should be jointly carried out by Railtel and field staff once in three months. A proper log/record of incidences of interruptions occurring in the sections should be maintained. SSE/JE of the section should also maintain the history of all the equipment failures and keep track of defective and working spare modules. ii. PROCEDURE FOR FAULT RECTIFICATION: ================================== a. When the fault is conveyed by NCC/Control Office, SSE/JE must consult NCC/Control Office to ascertain the exact nature of fault and plan the rectification in coordination with the NCC, mobilize the maintenance team and proceed to the site of interruption by fastest means. b. After reaching the site, OTDR testing may be done on short haul fibers from either side of the cable hut on both sides from the nearest OFC POP for localization of the fault as close as possible. c. Fault rectification shall be taken up in such a manner that working fibers are made through from both ends and link restored first and then proceed ahead to restore the remaining fibers. Splicing of fibers should be done in the prescribed order. It should not happen that only a few fibers are restored while others are not attended. Testing shall be done and SSE/JE should personally satisfy himself that the work has been done properly. d. During an OFC outage, the prime goal of the SSE/JE shall be to restore the link. In case fault localization becomes difficult due to site conditions, the link should be made through by temporarily patching the OFC/mechanical splice or by laying OFC on the ground or by use of aerial OFC, so as to minimize the outage. 13. SCHEDULE OF INSPECTION AND MAINTENANCE ====================================== i. Inspection of each equipment will have to be done thoroughly keeping time for it. A normal or casual visit for any other reason will not be treated as inspection. An inspection register will be kept at each location wherein inventory shall also be recorded with date of inspection. The brief inspection note shall be recorded by visiting officers. Compliance of the inspection notes should also be recorded by SSE/JE. Indoor equipment for long haul and short haul links shall be inspected and recorded. Following minimum schedule shall be followed. ii. Every indoor location -- (ADSTE/DSTE/Sr.DSTE) ============================================= - Electronics : Yearly - Checking of proper functioning : Yearly of external alarms - DG sets (if provided) : Yearly - Air conditioning : Yearly - Earth : Yearly - Fire alarm system : Yearly - Link status/loss auditing : Yearly - Testing of alarms and its : Yearly appearance on NMS iii. Section Incharge -- (JE/SSE) ============================ - Electronics : Monthly - Power supply equipment : Monthly - DG set : Quarterly - Air conditioning : Quarterly - Earth : Half yearly - Fire alarm system : Quarterly - General upkeep of equipment : Quarterly room - Checking of proper functioning : Quarterly of external alarms Periodical Checks and Preventive Maintenance ============================================ Electronics =========== b. Battery charger =============== - Testing of auto changeover of SMRs - Current setting as per load - Checking of input and output voltages - Reporting of alarms to NMS - Proper connection of input and load cables - Other checks as prescribed in the manual c. Battery set =========== - Checking of electrolyte level/gravities in case of low maintenance battery sets. - Checking of cell voltages and battery voltage at equipment end. - Cell whose voltage is found to be below prescribed value by the manufacturer should be noted and immediate corrective action taken for their replacement. - Checking of sulfation/physical damage - Testing of AH capacity (During installation and periodically as decided by the Railway) - Proper connection of load cables. d. Diesel Generator Set, wherever provided ======================================= - Testing on load - Testing of auto start in case of AC failure - Checking of hour meter readings - Checking of diesel oil/engine oil level - Checking of oil/air filters - Battery voltage (self start) - Cleanliness - Water level (in radiator) if applicable - Any other check prescribed in the manual e. Air Conditioning ================ - Working of the air conditioners - Working of changeover arrangement, if provided f. Earthing ======== - Watering of the pits - Checking integrity /continuity of the physical connections including at equipment ends. - Tightening of nuts/bolts - Checking of earth resistance (value should be less than 1 ohm preferably) g. Fire Alarm System ================= - Cleaning of fire sensors - Simulate the fire situation by applying smoke near to sensors. - See the fire panels for reports and analysis h. General Upkeep of co located equipment ====================================== - Ensure cleanliness - Ensure the tower maintenance is done as per schedule by the nominated agency. Annexure A ========== **Unit** -- -- -- ---------- -- -- -- Amp AH Litre Hrs ANNEXURE -- B ============= -- -- -- -- -- -- -- -- -- -- -- -- -- -- ANNEXURE -- C ============= -- -- -- -- -- -- -- -- -- -- -- -- -- -- ANNEXURE -- D ============= -- -- -- -- -- -- -- -- -- -- -- -- -- -- ANNEXURE -- E MAINTENANCE FORMAT FOR FIBRE OPTIC SYSTEM ======================================================= -- -- -- -- -- -- -- -- -- --