Shure 450 User Manual

Model 450 series ii user guide, Features, Press-to-talk switch operation

SHURE MODEL 450 SERIES II

PAGING AND DISPATCHING MICROPHONE

The Shure Model 450 Series II is a high output dynamic mi-

crophone designed for paging and dispatching applications.

This extremely rugged microphone features an omnidirec-

tional pickup pattern and a frequency response tailored for

optimum speech intelligibility. It also includes an impedance

selection switch and a locking press-to-talk switch. The

press-to-talk switch can be converted to a monitor/transmit

switch with the Shure RK199S Split-Bar Conversion Kit.

Features

•

Dual impedance

•

Locking press-to-talk switch

•

Rugged ARMO-DUR

base and case

•

Adjustable height

•

Optional monitor/transmit switch conversion kit

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, release 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 re-

lease it.

IMPEDANCE SELECTION

To select high or low impedance, move the impedance selec-

tion 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 Ω) microphone line to a high impedance

amplifier input.

WIRING CONNECTIONS

Refer to Figure 1 and Table 1 below. For unbalanced opera-

tion, 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, au-

dio 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 chas-

sis ground.

WHITE

GREEN

SHIELD

BLACK
RED

IMPEDANCE SWITCH

PRESS-TO-TALK SWITCH

1 2

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

GREEN

AUDIO

PIN 2

TIP

UNBALANCED

WHITE

AUDIO GROUND

PIN 3

SLEEVE

SHIELD

CHASSIS GROUND

PIN 1

SLEEVE

GREEN

AUDIO +

PIN 2

TIP

BALANCED

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 closure may be used to con-

trol an external relay or a transmit/receive circuit.

CHANGING PTT CIRCUIT TO NORMALLY OPEN

Using microphones in parallel requires a normally open mi-

crophone 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.

Model 450 Series II User Guide

C2917 (Rev. 3)

2005, Shure Incorporated

Printed in U.S.A.