Maxim Integrated 73M1822/73M1922 Control Module - Manual (Page 12)

73M1822/73M1922 Control Module User Guide UG_1x22_053
12 Rev. 1.0
2.2.5 Loopback and Testing Modes
The 1x22 devices support several variations of loopback modes. Refer to the “Loopback and Testing
Modes” section of the 73M1822/73M1922 Data Sheet for more detail. Each loopback mode is designed
to test connectivity at various points in the system. Systematically use of the loopback feature in
conjunction with external application that control data stream in and out of the system can be an effective
tool to isolate faults. While the driver provides IOCTLs to manage those loopback test points, it does not
have a way to inject or intercept data flow through the system to perform diagnostic. It relies on external
application for those capabilities. The IOCTL for managing the loopback can be found in
Section 6.8.1 .
2.2.6 Call Progress Monitor
The 1x22 device provides the ability to monitor activity on the line via feature called the Call Progress
Monitor. The gain setting of its audio path can be adjusted using the M1X22_CPROG_MONITOR IOCTL
detailed in
Section 6.9.3 . For more detail on this subject, refer to the “Call Progress Monitor” section of
the 73M1822/73M1922 Data Sheet.
2.2.7 Billing Tone Filter
Some countries use a large amplitude out-of-band tone to measure call duration and to allow remote
central offices to determine the duration of a call for billing purposes. To avoid saturation and distortion of
the input caused by these tones, it is important to be able to reject them. These frequencies are typically
12 kHz and 16 kHz. Refer to section “Billing Tone Rejection” in the 73M1822/73M1922 Data Sheet for
more detail.
To enable or disable the billing tone filter, the driver offers the M1X22_BTONE_FILTER IOCTL. Its
description can be found in
Section 6.9.2 .