Model 550L User Guide
Shure Brothers Incorporated
222 Hartrey Avenue
Evanston IL 60202-3696 U.S.A.
27A8090 (RB)
E1998, Shure Brothers Incorporated Printed in U.S.A.
MODEL 550L
OMNIDIRECTIONAL DYNAMIC
BASE STATION MICROPHONE
The Shure 550L is a dynamic base station micro-
phone with a frequency response specially tailored for
voice intelligibility. It is equally useful for radio commu-
nications, paging and dispatching systems, and its
low-impedanceconnectionmakesitadaptabletomost
PA amplifiers. The low-impedance design also makes
itusefulforlongruns,orunderseverehumdisturbance
conditions.
Themicrophoneisnotaffectedbyheatorhumidity.
Its exclusive ARMO-DURRcase is immune to oil,
grease, fumes, salt spray, sun, rust, and corrosion
—and is outstanding in its ability to resist mechanical
shocks and vibration. The “Million-Cycle” leaf-type
switch is designed to withstand rigorous operating
conditions and constant use.
Features
•
Low-impedance operation for long cable runs or
severe hum disturbance
•
Crisp, natural, high-intelligibility voice response
•
Fingertip control bar actuates microphone circuit
and external relay or control circuit
•
Long-life switch meets rigorous requirements of
communications and paging systems
•
Sturdy, high-impact ARMO-DUR base and micro-
phone case—impervious to corrosion
•
Reliability plus—under all operating conditions
•
Neoprene feet prevent microphone slipping
PRESS-TO-TALK SWITCH OPERATION
The fingertip control bar is a non-locking switch;
simply depress the control bar and release after trans-
mission.
CONNECTIONS
Figure 1 shows the internal wiring of the 550L
microphone. The 550L is designed for balanced-line,
low-impedance operation. The WHITE and GREEN
cableleads arethe twoconductors forthe microphone
circuit; the shield is connected to the amplifier or chas-
sis ground. The RED and BLACK leads control an ex-
ternal relay or switching circuit.
RED
ORANGE
RED
BLACK
WHITE
GREEN
SHIELD
TRANSMIT
INTERNAL CONNECTIONS
FIGURE 1
Low-impedance operation is extremely useful
wherelongcable lengthsarerequired, or undercondi-
tions of severe hum disturbance. The permissible
cable length is practically unlimited, since neither re-
sponse nor level is appreciably affected. Shure A95
Series Line Matching Transformers are available for
use in those cases where a low-impedance micro-
phone is to be used with an amplifier with a high-
impedanceinput.Thesetransformersprovideaproper
impedance match between a 19- to 300-ohm micro-
phone and a high-impedance input, and are available
with various input and output connectors.
