CM1481 Datasheet, PDF (15/24 Pages) ON Semiconductor – 2-Channel EMI Filter with ESD Protection for Headsets/Speakers

Functional Descriptions ......
Input/Output
Polarities
The following input and output activation polarities may be set at configuration.
Function
Notes
On-Board State
PTT In
Tx On
Input
Output
Pullup to V_DD
Busy
Mute Ctrl
Input
Output
Pullup to V
DD
LED
Output
Quiet/Open
Tx Call
Input
Input
Pullup to V_DD
Pullup to V_DD
Table 6 Input/Output Programmable Polarities
Connected To
- the microphone end of the radio PTT line
- the PTT line to the Tx circuitry
- Rx carrier detect circuitry
- to operate the radio squelch gate
- to drive an LED to provide a visual alert
- to control the radio mute state
- Selcall initiation
Tx Timeout
and
Warning
To prevent nuisance and to regulate transmissions to a reasonable period, the PTT
Timeout function will disable all PTT Tx functions after a pre-determined (configured) time
period.
When the PTT is activated the PTT Timer will run for the configured interval giving an
Audible Warning 6-seconds before the timeout. If the PTT is still active 6-seconds after
the warning the transmission will be aborted at that time and all PTT functions completely
disabled for a short period (6-seconds) to enable other users the opportunity to enter the
channel.
Although not recommended, if the the PTT is released and re-keyed frequently before the
PTT Timeout Warning, the PTT Timer will be reset and the Tx Timeout will not be
activated
Under Tx Timeout conditions, the PTT must be released and will not be re-enabled for a
predetermined period. The PTT Timeout period can be configured to OFF.
Configured as PTT Time-Out:
NOTONE Timer
A configurable function incorporated to indicate the end of a tone or tone sequence to the
on-board µController. For optimum CM1481 performance it is recommended that this
function be set to approximately 1.5 times the selected Tone Length.
Configured as NOTONE Timer:
Recommended NOTONES
Toneset
EEA
CCIR
ZVEI
Tone Length
40ms
100ms
70ms
NOTONE Period
60ms
160ms
100ms
Transpond-
ing
In reply to a Selcall the CM1481 can be configured to respond by transmitting either its
Transpond Address (Tp) or a BEEP (tone F). This function can be re-configured over-air.
Configured as Transpond Mode: and Transpond Address:
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