Functional Descriptions ......
The following input and output activation polarities may be set at configuration.
Input/Output
Polarities
Function
PTT In
Tx On
Notes
Input
On-Board State
Connected To
Pullup to VDD
- the microphone end of the radio PTT line
- the PTT line to the Tx circuitry
- Rx carrier detect circuitry
Output
Input
Busy
Pullup to VDD
Mute Ctrl
LED
Output
Output
Input
- to operate the radio squelch gate
- to drive an LED to provide a visual alert
- to control the radio mute state
- Selcall initiation
Quiet/Open
Tx Call
Pullup to VDD
Pullup to VDD
Input
Table 6 Input/Output Programmable Polarities
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.
Tx Timeout
and
Warning
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:
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.
NOTONE Timer
Configured as NOTONE Timer:
Recommended NOTONES
Toneset
EEA
Tone Length
40ms
NOTONE Period
60ms
CCIR
ZVEI
100ms
160ms
70ms
100ms
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.
Transpond-
ing
Configured as Transpond Mode: and Transpond Address:
15
CMLMICRO [ CML MICROCIRCUITS ]
