27C2917 (Rev. 5)
Printed in U.S.A.
©2012 Shure Incorporated
Model 450 Series II
User Guide
SHURE MODEL 450 SERIES II
PAGING AND DISPATCHING MICROPHONE
The Shure Model 450 Series II is a high output dynamic micro-
phone designed for paging and dispatching applications. This
extremely rugged microphone features an omnidirectional pickup
pattern and a frequency response tailored for optimum speech in-
telligibility. It also includes an impedance selection switch and a
locking press-to-talk switch.
Features
•
Dual impedance
•
Locking press-to-talk switch
•
Rugged ARMO-DUR
®
base and case
•
Adjustable height
PRESS-TO-TALK SWITCH OPERATION
To operate the control bar as a press-to-talk switch, simply hold
it down and begin speaking. When you are finished speaking, re-
lease the control bar.
To lock the control bar in the “on” position, press it down and pull it
forward. To unlock the control bar, push it back and release it.
IMPEDANCE SELECTION
To select high or low impedance, move the impedance selection
switch, located under the microphone base, to either the HIGH or
LO position. The switch is factory pre-set to LO.
Shure recommends the low impedance setting if long lengths of
cable are used, or if severe hum is encountered. Use Shure A95
Line Matching Transformers to match a low impedance (300
W
)
microphone line to a high impedance amplifier input.
WIRING CONNECTIONS
Refer to Figure 1 and Table 1 below. For unbalanced operation, the GREEN
wire is connected to the audio input, the WHITE wire is connected to the audio
ground, and the SHIELD is connected to chassis ground. In some cases, audio
ground and chassis ground will be the same.
For balanced operation, the GREEN wire is connected to the positive audio
input, the WHITE wire is connected to the negative audio input, and the SHIELD
is connected to chassis ground.
HI
LO
WHITE
GREEN
SHIELD
BLACK
RED
IMPEDANCE SWITCH
PRESS-TO-TALK SWITCH
1 2
3
GREEN
WHITE
GREEN
ORANGE
RED
YELLOW
BLACK
WIRING DIAGRAM
FIGURE 1
Table 1. Typical Cable-to-Connector Wiring
INPUT TYPE
WIRE
COLOR
FUNCTION
XLR
CONNECTOR
1/4 IN.
PHONE
JACK
UNBALANCED
GREEN
AUDIO
PIN 2
TIP
WHITE
AUDIO
GROUND
PIN 3
SLEEVE
SHIELD
CHASSIS
GROUND
PIN 1
SLEEVE
BALANCED
GREEN
AUDIO +
PIN 2
TIP
WHITE
AUDIO -
PIN 3
RING
SHIELD
CHASSIS
GROUND
PIN 1
SLEEVE
NOTE:
The RED and BLACK leads are not part of the audio circuit. These wires
provide a contact closure when the press-to-talk switch is depressed. This clo-
sure may be used to control an external relay or a transmit/receive circuit.
CHANGING PTT CIRCUIT TO NORMALLY OPEN
Using microphones in parallel requires a normally open microphone circuit. To
modify the press-to-talk switch so that it provides a normally open circuit, proceed
as follows:
1. Remove the screws, washers, and bottom plate from the microphone.
2. Unsolder the black, red, and white leads from the terminal of the press–
to–talk switch (see Figure 1). Make sure these leads are still soldered
together. If necessary, resolder them and insulate the connection.
3. Replace the bottom plate and secure it with the screws and washers
removed in Step 1.
