Specifications

Chapter 7 Battery Reversal FXS/DPO
7-8
SETTING BRFXS AND DPO TERMINATIONS
Battery Reversal FXS Loop-Start
The BRFXS/DPO card includes a setting for 2-wire FXS loop-start operation with battery reversal. To
enable this option, set Switch A on the 4-position DIP switch to ON so that cadenced ringing voltage is
applied to the CPE loop during an incoming call. See Table 8-2. The battery is reversed during this time.
If desired, Switch B can be turned ON also to send a cadenced (2-second/ 4-second) ringback tone to the
T1 line during incoming calls.
Dial Pulse Origination (DPO)
The DPO termination option is selected by setting Switch A to 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. See Table 8-2. To indicate an incoming call, the battery to the
CPE loop is reversed. When the call ends, the battery returns to forward.
BRFXS/DPO Voice Channel Monitoring and Testing
The channel status LEDs on the back plate of the Access Bank I allow you to monitor the individual
BRFXS/DPO voice lines. The meaning of these LEDs is summarized above in Figure 8-5.
The channel test switches on the BRFXS/DPO back plate can be used to apply reverse battery to the CPE
loop and send A/B bits forced to 1/1 toward the T1 network. If Switch A is ON, 4 seconds of continuous
ringing voltage (85 V) are sent to the tip and ring pair of each BRFXS/DPO voice channel. In this case,
you can check the operation of an individual voice channel by attaching a test telephone to the Tip and
Ring pair of that particular channel at the punchdown block or RJ-11 Harmonica, then switching ON the
appropriate channel test switch to test that channel. If Switch B is ON, 4 seconds of continuous ringback
tone is also sent to the T1 network.
“BUSYING OUT” INDIVIDUAL BRFXS/DPO CHANNELS
If Switch A and Switch B are both ON, setting a channel test switch to ON has four results on the selected
channel:
1. Reverse battery is applied to the CPE loop and the A/B signaling bits sent to the network are
forced to 1/1.
2. To confirm individual channel circuit integrity, 4 seconds of continuous ringing voltage are sent to
the Tip and Ring pair. The Tip is then grounded until the channel test switch is turned to the OFF
position (to the right).
DANGER! Four seconds of continuous ringing voltage (85 V) will be present at the Tip and Ring
pair of the channel-under-test until the test telephone is picked up to trip the ringing.
Requirement: A test telephone connected to the punch down block or RJ-11 Harmonica should
ring for 4 seconds.