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Optimized Utilization of PHC Terminals in VU

The only growth element in VU is the SHM card. The SHM card contains Protocol Handler Controller (PHC) terminal, which can be configured as signallinig terminals or internal message protocol (C.85) terminals. Out of the 8 PHC terminals available in one SHM card, two (2) C.85 terminals are used for internal message communication of the VU with the processor of the BM in which it is equipped. The remaining terminals are available for utilization of C-Channels for each AI interface to be created. Two terminals per AI will be utilized, if both primary and secondary links are created. In case if single link is used for every AI interface, one terminal per AI will be allotted.

The utilization of c.85 terminals for C-Channels is governed by the system parameter "V5-THR". The default value of this parameter in BMDC is 50 (percent). Hence, out of eight (8) C.85 terminals in one SHM card, four (4) terminals can be used for C-Channels for AI interface and the remaining four (4) terminals are utilized for internal message communication of the VU with the processor of the BM in which it is equipped.

Normally we equip two (2) SHM cards in a VU, with a total of sixteen (16) terminals. Let us make the value of the system parameter "V5-THR" as 75. Then twelve (12) terminals are configured as C-Channels and the balance four (4) terminals are configured as C.85 internal communication purpose. Now a maximum of twelve (12) AI interfaces with single link can be created. In case of any part of the SHM card goes faulty four (4) terminals become oos-se and out of the balance twelve (12) terminals , we get only nine (9) terminals for C-Channel and the result is any of the tree (3) AI interface will go down.

When more than eight (8) AI interfaces are planned at your Exchange, it is very much suggested that three (3) SHM cards are to equipped in your VU. With the result , a total of twenty four (24) terminals are available . Out of 24 , eighteen (18) terminals are configured for C-Channels toward AI interface and the rest of the six (6) terminals are configured for internal communication. Now if a card becomes faulty or portion of the SHM card becomes faulty will not affect the performance of AI working.

Hence it is suggested to have three (3) SHM cards and System parameter for "V5-THR" as 75 and VU-INT-THR as 25 for optimum utilization .