Lectrosonics H187 - Manual (Page 5)

Plug-On Transmitter
Rio Rancho, NM 5
TOP VIEW CONTROL PANEL
LIMIT LED
LEVEL LED
ON OFF LEVEL
MUTE
BATTERY
POWER
LED
Controls and Functions
The H187 may be used with a wide variety of micro-
phones. The 3-pin XLR type connector on the H187
allows the transmitter to be used with any dynamic
microphone, as well as many two wire positive bias
lavaliere systems (such as those systems supplied by
Lectrosonics.)
Input Jack
Standard 3-pin Switchcraft XLR type. Pin 2 is signal,
pin 3 is signal ground, and pin 1 is case ground (see
schematic below). The H187 is self-locking onto a
standard microphone. The XLR connector is perma-
nently bonded to the metal collar, and is not normally
replaceable. The electret bias is 5 Volts at 1mA or less.
The bias is connected in a “phantom” manner and will
not interfere with any standard balanced microphone. If
severe noise is experienced when the microphone is
moved with respect to the H187, the cause is an
unbalanced condition between pins 2 and 3 of the
microphone.
Input Jack Schematic
Power/Mute Switch
Turns the battery power on and off. The center position
is an “audio mute” which should be used when setting
the MIC LEVEL control. The “mute” position discon-
nects the audio signal from the transmitter and allows
you to adjust the audio modulation level without the
possibility of feedback. When turning the transmitter
on, pause for a moment in the “mute” position. This will
prevent a turn-on surge from occurring (a “thump”
sound).
Power On/Off LED
Glows brightly when battery is good. A weak or dim
LED means that the battery is weak, and has about an
hour of operation left. If the LED fails to light, the
battery should be replaced. The power LED should
light up in both the “mute” and “on” positions of the
POWER/MUTE SWITCH.
1 UH
1K 1K 980
+9 VOLTS
1 2
3
33UF 5.1V
TO MIC
PREAMP
AUTO-LOCK
XLR INPUT
1 UH
1 UH
The POWER LED is connected to a precision battery
test circuit that continuously monitors battery voltage.
The LED is at full brightness with a new 9 Volt alkaline.
As the battery voltage drops during use, the LED
brightness will also decrease. After 12 to 15 hours the
battery voltage will be about 7 Volts. The LED will be
completely extinguished. Since the internal circuits are
all tightly regulated and the RF output stage has a
separate discrete regulator, the transmitter will continue
to operate to a battery voltage of 6.5 Volts. From 6.5
Volts to 6 Volts, the transmitter will still operate, but with
degraded performance. Please note that a weak
battery will sometimes light the POWER LED immedi-
ately after turn on, but soon will discharge to the point
where the LED will extinguish.
The combination of an accurate battery condition
indicator and regulation of all internal circuits guaran-
tees much longer battery life, as well as consistent
performance versus battery life.
Modulation LEDs
Indicate the proper setting of the MIC LEVEL control.
Level LED
Flickers or glows all the time if the audio volume is
adequate for normal operation.
Limit LED
Lights up when the audio volume is high, indicating that
the signal level is being limited by the compressor.
Optimum signal-to-noise ratio is obtained when the limit
LED lights occasionally.
Mic Level
Used to adjust the audio input volume for the proper
modulation level. Rotate knob until the LEVEL LED
flickers when there is an input signal. The LIMIT LED
should light occasionally.