Carrier Access SNMP manual Overview of Operation

Battery Reversal FXS & Dial Pulse Origination Card

provides twelve 2-wire CPE analog loop-start connections to the digital T1 line using the same method used by the FXS voice card, only with the addition of Tip/Ring battery reversal. The FXS interface reverses the polarity of the battery feed towards the customer premise equipment (CPE) in response to the signaling bits coming from the T1 line. Various PBX systems require battery reversal to signal the start of billing, and in certain telephony environments it is needed to provide Line Side Answer Supervision (LSAS). One important application for battery reversal occurs in International Call Back, which allows international callers dialing the US to avoid more expensive inbound rates by taking advantage of cheaper US outbound long distance rates.

Dial Pulse Origination (DPO) is the functional complement to Dial Pulse Termination (DPT) pro- vided by the FXO/DPT voice card. Used in conjunction, the DPO and DPT cards are used mainly for origination and termination of Direct Inward Dial (DID) circuits.

The BRFXS/DPO is a 7.8” by 13.16” daughter card designed to slide into the back of the Access Bank II along rails that guide a 64-pin DIN connector to mate with a matched connector on the inter- nal ABI Controller. The card receives the T1 signaling, tip and ring pairs, control logic and power from the Controller card through this connector. The back plate of the card has 12 channel status LEDs and one 4-position DIP switch for selecting between battery reversal FXS loop-start and Dial Pulse Originating (DPO) modes of operation. Furthermore, the back plate also contains 12 test switches that can be used to “busy out” each channel individually. On the BRFXS/DPO card itself, each individual channel has a 6-position DIP switch for setting transmit and receive line attenuation.

9.3 Overview of Operation

The reversible-battery FXS channel card is designed to provide twelve 2-wire analog interfaces to the digital T1 (DS1) line. Currently, the analog loops (also called CPE loops in this document) must always be loop-start.

One of the main features of the analog interface is that the polarity of the battery feed towards the customer-premise equipment (CPE) can be reversed in response to the signaling bits coming from the T1 line.

•The basic operation is selected by setting Switch A off so that no ringing voltage is applied towards the CPE. If desired, Switch B can be turned on to give a cadenced (2- second/4-second) ringback tone to the T1 line during incoming calls. The battery to the CPE loop will be reversed to indicate an incoming call. The battery will return to forward polarity again when the call has ended.

•Also included in this channel card is a setting to provide cadenced ringing voltage (if needed by other customer-premise equipment). This option is enabled by setting Switch A on so that cadenced ringing voltage will be applied to the CPE loop during an incom- ing call. The battery is reversed during this time. If desired, Switch B can be turned on to give a cadenced (2-second/4-second) ringback tone to the T1 line during incoming calls, that is synchronized to the ringing voltage present on the loop.

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