CM1481 Datasheet, PDF (16/24 Pages) ON Semiconductor – 2-Channel EMI Filter with ESD Protection for Headsets/Speakers

Functional Descriptions
Lead-In
Delay
A configurable delay period between the operation of the PTT and the Selcall Tone output
from the module. This function is available to allow sufficient time for the transmitter to
stabilize before modulation.
Configured as Lead-In Delay:
Lead-In Delay
PTT Out
(active "low")
Lead-In
Delay
Tone Out
Selcall Tones
Lead-In Tone with No Gap
Tone Out
Lead-In
Tone
Selcall
Tones
Lead-In Tone with Gap -- the gap is 1 tone-length
Tone Out
Lead-In
Tone
Selcall
Tones
Fig.9 Lead-In Tone and Delay
Lead-In Tone
To operate on and gain access to, repeater systems the Selcall address output of the
module can be preceded by an extended tone. At configuration the tone operation, fre-
quency and length can be set; if required a single Selcall tone-period gap between the
lead-In tone and the Selcall address may be set.
Configured as Lead-In Tone Length:, Lead-In Tone Digit: and Lead-In Gap:
Quiet/Open
Modes
The CM1481 has two audio operational modes - ‘Quiet and Open’.
Quiet/Open operations are initiated by:
(i) Pressing the Quiet/Open button (Dual Button operation) or a short press of the
Operate button (Single Button operation).
Quiet operations are initiated by:
(i) A Timed Mute Reset operation.
(ii) A Remote Reset command received.
Quiet
The radio Rx audio is muted.
PTT (Tx) action is disabled.
Selcalling can either be disabled or enabled via initial configuration. There are no operational
alerts except for PTT and Call Action Disabled or Selcall Transmitted (if configured).
Open
Open modes can be configured to either Unmuted or Transparent states.
If called in an “Open” mode received Selcall tones will be output at the loudspeaker.
Configured as Open Mode:
Unmuted:
The radio is unmuted (MUTE CTRL inactive) and the loudspeaker (hash) is enabled. All
functions are enabled and operate as configured.
Transparent:
The radio audio circuits act as if squelched; Audio output is dependant upon the presence
of an RF carrier (BUSY input). MUTE CTRL is only inactive if the BUSY input is active.
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