LEVEL SETTING AND INTERFACE ADJUSTMENTS
To accomplish level setting and any changes in (jumper) options, remove the four
screws and the microphone back cover.
Jumper JP1 - Audio Gain Select Jumper
This jumper is used to set the range of microphone and DTMF audio output from the
600L microphone. When JP1 is installed (factory default, as shipped), it will
accommodate requirements where the microphone audio is in the range of 40 mV or
less. For higher voice and DTMF tone input levels, remove JP1.
DTMF Tone Output Level (RV1)
For reliable DTMF signaling: The DTMF tone deviation should be approximately 2/3 of
the maximum deviation (for example: if the modulation limiting is set to 5.0 kHz, then
the DTMF level should be 3.3 kHz). In any event, the DTMF Tone transmitted by the
600L microphone should not be clipped or distorted. If your service monitor does not
have a CRT display to observe the transmitted waveform, use an oscilloscope
connected to the "demod" output from the service monitor to visually verify the quality
of this signal. Set RV1 for the proper DTMF Tone level (3.3 kHz).
For applications
where a 2.5 kHz deviation limit is used, set the DTMF level to approximately 1.7 kHz
with no CTCSS tone, or 2.2 kHz with CTCSS tone.
If the output is insufficient for
proper modulation deviation, then remove JP1.
Voice Level Adjustment (RV2)
This adjustment sets the microphone level for voice modulation only. While monitoring
the transmitter frequency on a service monitor, press the microphone PTT switch and
set RV2 on the 600L microphone so that the voice deviation peaks just before limiting
(clipping) occurs while speaking in an average voice level. Remove JP1 if the proper
modulation level cannot be reached.
Tone Burst Mode
The 600L microphone is shipped for the continuous DTMF tone mode. This mode
provides a DTMF tone for the duration that the user presses a key. For the Burst Mode
option, where a fixed length DTMF tone burst of 150 milliseconds is desired, install
jumper JP4 (shown on figure "A").
Automatic Push-To-Talk (PTT)
The 600L microphone is shipped with Automatic Push-To-Talk enabled, where PTT
occurs upon depressing any keypad digit. Should the application require that the user
press the PTT switch in order to encode DTMF dialing, then remove resistor R2 (10K)
to invoke this operation, and disabling the Automatic PTT feature. See Figure "A" for
the location of R2. If R2 is removed, sidetone audio will not be heard from the
microphone during DTMF dialing.
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