CM1481 Datasheet, PDF (13/24 Pages) ON Semiconductor – 2-Channel EMI Filter with ESD Protection for Headsets/Speakers

Functional Descriptions ......
Audio Alerts
The CM1481 will provide 'alert' output signals to be used in an audio system to indicate
and highlight certain operations; these are described below.
The alert output signal takes the form of a square-wave at the frequencies and durations
described.
It is recommended that the Alert output is introduced to the receiver audio amplifier stages
after the squelch gate and with due regard to any audio powersave functions.
To facilitate either loudspeaker or amplifier operation, a removable LINK is provided on the
CM1481 PCB. To drive a loudspeaker, leave the LINK in place. To interface with an
external amplifier, remove the LINK (see PCB Layout, Figure 4).
Cause of Alert
Alert Description
Entering ‘Quiet’ condition Short duration low-pitch beep
Frequencies
1 x 200ms at 250Hz
Entering ‘Open’ condition Short duration high-pitch beep
1 x 200ms at 1kHz
Selcall Received
A train of rapid mid-pitch beeps
(‘n’ configured as “Called Alerts”)
cancelled by a PTT, CALL or QUIET/OPEN action ‘n’ x 200ms at 1.25kHz
[+ activation of LED output.] See LED Call Memory
GROUP Call received 3 short duration mid-pitch beeps
3 x 200ms at 750Hz
Selcal transmitted
Short duration mid-pitch beep
1 x 100ms at 500Hz
Tx Time-out warning Short duration high-pitch beep
1 x 100ms at 1.5kHz
PTT action disabled
Continuous low-pitch tone
347Hz
CALL action disabled Continuous low-pitch tone
347Hz
Table 5 Audio Alert Descriptions
PTT Lockout
An internal operation carried out by the CM1481 that will prevent the Tx On line being
placed in an active condition irrespective of the state of the PTT In input.
Conditions that cause a PTT Lockout are:
• An active ‘BUSY’ input.
• The CM1481 in the ‘Quiet’ (muted) condition.
• PTT Timeout expired and not reset.
Automatic
REPEAT-
Tone
If in any tone sequence (address or data) one tone character is identical to the preceding
one, to prevent confusion at the decoder a REPEAT-tone (‘E’) must be transmitted in its
place.
At configuration the CM1481 addresses are entered using the code characters ‘0’ thro ‘A’
and identical characters entered as required.
The PC software then processes the address inserting REPEAT-tones as necessary
before writing the information to the module. The REPEAT-tone must not be used as the
first character of a sequence; Address/Data tones received by the CM1481 must conform
to the REPEAT-tone rule for complete decode accuracy.
Example:
Required Sequence
Transmitted Sequence
12335
123E5
Timed Mute
Reset
When configured this function will automatically close (re-mute) the CM1481, if in the Open
mode, after the configured time-period of inactivity.
Configured as Timed Mute Reset:
13