Shure 550T User manual

1
OMNIDIRECTIONAL PREAMPLIFIED DYNAMIC BASE STATION MICROPHONE
Note: After unpacking the microphone, remove
the protective film from the nameplate
MODULINKSYSTEM I
GENERAL
The Shure 550T and 550TSB Series II Modulink Base
Station Microphones are rugged, omnidirectional dynam-
ic microphones with a built-in preamplifier. Designed for
optimum voice clarity, they can replace dynamic or ceram-
ic, high- or low-impedance microphones supplied as origi-
nal equipment. Both models provide radio communica-
tions, paging and dispatch systems with clear, high output
voice transmission, even in noisy environments.
The 550T and 550TSB Series II are MODULINKuni-
versal replacement microphones. They are compatible
with a variety of five-conductor, shielded, coil-cord cables
(sold separately), each of which has a locking, telephone-
type modular plug on the microphone end. One cable type
has bare tinned leads on the transmitter input end so that
the user can install any desired connector. Since cable
damage is the major cause of microphone failure, this in-
novation allows economical, quick and simple repairs.
The 550T and 550TSB Series II microphones have ex-
tremely low sensitivity to hum pickup and low susceptibility
to rf interference. A built-in preamplifier makes them com-
patible with biased-audio (powered audio) radio commu-
nications systems. An externally accessible microphone
sensitivity control, located under the base, allows the op-
erator to adjust the output level. If desired, the preamplifier
can be bypassed and the microphone can be operated in
the direct output (non-amplified) mode.
An especially useful feature for shared-channel radio
systems using the Continuous Tone Coded Squelch Sys-
tem (CTCSS) is the split-bar Press-to-Talk (PTT) switch.
The Transmit side of the switch can only be actuated when
the Monitor side of the switch is depressed, so the opera-
tor is forced to verify that the channel is clear before trans-
mitting. The Monitor switch can also be locked into the “on”
position, if desired, by sliding it forward.
The 550TSB Series II microphone is functionally and
electronically identical to the 550T Series II, but it has a
single PTT switch instead of a split bar PTT switch. The
550TSB Series II can be used with trunking or other radio
systems which do not require the channel monitoring.
Both microphones are ergonomically designed; the
pushbuttons and grasping surfaces conform naturally to
the hand. The virtually indestructible ARMO-DURcase
is immune to oil, grease, most fumes and solvents, salt
spray, sun, rust and corrosion. It is outstanding in its ability
to withstand mechanical shock and vibration.
The microphones’ Million-Cycle-Plusleaf switch is de-
signed for constant use even under extreme conditions.
Its nickel-silver plated blades and palladium alloy con-
tacts resist oxidation for years.
Features
•Modular-plug coiled cord—easily changed for other
radio sets or to replace defective cable. A genuine uni-
versal replacement microphone
•Built-in preamplifier with convenient external gain ad-
justment
•Dynamic cartridge with omnidirectional pickup pattern
•Frequency response tailored for optimum speech in-
telligibility, and clear, crisp response
•Low sensitivity to rf interference and hum pickup
•Rugged, lockable PTT switch stands up under severe
environments and constant use
•High-impact ARMO-DUR case is stronger and lighter
than die-cast metal
Model 550T and 550TSB Series II Modulink
Base Station Microphone User Guide
27B3024 (Rev. 7)
2004, Shure Incorporated Printed in U.S.A.

2
MODIFICATION
The Monitor switch as provided is normally closed for ra-
dios with scanning or CTCSS functions that open when
the switch is depressed. For radios that require a normally
open (closed circuit when the microphone Monitor switch
is depressed) such as many Ericsson/GE models, per-
form the following modification.
1. Remove the baseplate by removing the screws secur-
ing it to the microphone.
2. Locate the yellow wire from the printed circuit board to
the monitor switch.
3. Unsolder the yellow wire from the top terminal of the
monitor switch and resolder it to the lower open termi-
nal of the monitor switch.
4. Replace the baseplate and screws.
MICROPHONE CABLES
The 550T Series II can be used with various MODU-
LINKmicrophone cables. Each cable has a modular mi-
crophone plug on one end and the user’s choice of equip-
ment plugs on the other. The MODULINK Cordset Table
supplied with the 550T Series II lists the most popular ra-
dios available and the cordset (ALM-) designed for use
with each. Note that the ALM-1 has no connector on the
equipment end; it can be wired as needed.
7 8
MODEL ALM-1 CABLE WIRING
FIGURE 1
The cable is attached to the 550T Series II by inserting the
modular telephone-type plug in the microphone jack until it
locks. To remove the cable from the microphone, insert the
small screwdriver supplied with the 550T Series II in bottom
case hole adjacent to the cable jack (see Figure 3) to unlock
the plug and withdraw the plug from the jack.
MICROPHONE CONNECTOR WIRING
Pin Color Function Pin Color Function
1 NC –– 5 Black PTT
Switch
Ground
2 Red Bias (+), DC
Audio Out
6 White Audio
3 Yellow PTT Switch 7 Drain Ground
4 Blue Monitor 8 NC ––
CONNECTIONS
The 550T Series II is designed to operate with two-way
radio sets with input circuits similar to those in Figure 2.
When wiring ALM-1 cables with connectors for radios not
listed in the table, modular connector pin 2 is to be used
for the dc bias resistor on the input.
PIN 2
1 K560
9.6 VDC
15 µF
PIN 7
FIGURE 2
ADJUSTING OUTPUT LEVELS
To adjust the output level, proceed as follows:
1. Insert a screwdriver into the sensitivity control poten-
tiometer, located in the microphone base (see Figure 3).
2. Rotate the control counterclockwise to increase sensi-
tivity or clockwise to decrease sensitivity.
SENSITIVITY
ADJUST
MODULINK
CABLE RELEASE
(CCW MAX.)
FIGURE 3
INTERNAL CONNECTIONS
The circuit board layout is shown in Figure 6 and the in-
ternal electrical connections are shown in Figure 7. A sche-
matic diagram of the circuit board is shown in Figure 8.

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SPECIFICATIONS
Test Conditions: (unless otherwise specified)
Audio output between pin 2 and Ground
Mic level trimmer full CCW
PTT switch depressed
Measured with High Z DMM
Standard test circuit as shown in Figure 2
Cartridge Type
Dynamic (with preamplifier)
Frequency Response
200 to 5,000 Hz (See Figure 4)
TYPICAL FREQUENCY RESPONSE
FIGURE 4
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+10
0
–10
RELATIVE RESPONSE IN dB
FREQUENCY IN HERTZ
Polar Pattern
Omnidirectional
Sensitivity (at 1 kHz)
Cartridge Direct Output:
–35.5 dBV (16.8 mV)/100 µbar
Amplified Output:*
–4 dBV (0.63 V)/100 µbar
*Using standard test circuit shown in Figure 1, with microphone sen-
sitivity adjustment trim potentiometer set to maximum (counter-
clockwise).
Hum Sensitivity
34 dB maximum equivalent SPL per 1 mOe, 60 Hz
electromagnetic field
Output Impedance
190 Ω direct output
Switches
Press-to-Talk: Double-pole, double-throw, leaf-type
switch; push-to-talk function normally open, cartridge
shunt normally closed
Monitor: Single-pole, double-throw, leaf-type switch;
normally closed
DC Supply Current
2.5 mA ±0.25 mA
Cable (optional choice)
Detachable, 1.2 m extended (48 in.), 5-conductor (1
shielded), Neoprene-jacketed coil cord with modular
plug on microphone end (see supplied Cordset Table
for available installed equipment plugs)
CERTIFICATION
Eligible to bear CE Marking. Conforms to European EMC Direc-
tive 89/336/EEC. Meets applicable tests and performance crite-
ria in European Standard EN55103 (1996) parts 1 and 2, for resi-
dential (E1) and light industrial (E2) environments.
Net Weight
736 grams (1 lb 10 oz)
Overall Dimensions (Figure 5)
FIGURE 5
FURNISHED ACCESSORY
Hardware Kit 90SJ1371. . . . . . . . . . . . . . . . . . . . . . . . . . .
REPLACEMENT PARTS
Cartridge Assembly R147. . . . . . . . . . . . . . . . . . . . . . . . . .
For additional service or parts information, please con-
tact Shure’s Service department at 1-800-516-2525. Out-
side the United States, please contact your authorized
Shure Service Center.

4
1. ALL RESISTORS 1/4 W, 2%, UNLESS OTHERWISE SPECIFIED.
2. ELECTROLYTIC CAPACITORS SHOWN IN µF X VOLTS.
NON-POLARIZED CAPACITORS IN µF, 10%, 50 V OR MORE UNLESS
OTHERWISE SPECIFIED.
3. R5 GAIN ADJUSTMENT FROM BOTTOM SIDE OF BOARD.
J5
C6 C3
R5
C8
C11
Q1
C2 R2
C1 C10
R4
R3
R1
C7
C9
L1 C4 C5
J3 J2 J1 J4
J7
J8
J6
J7
J8
J6
J5 J3 J2 J1 J4
123 45
BLACK WHITE
BLACK WHITE GREEN
RED
ORANGE
BLUE
GREEN
YELLOW
RED
ORANGE
YELLOW
Transmit Monitor
WHITE
SHIELD
CARTRIDGE
FIGURE 6
FIGURE 7
FIGURE 8
NOTES:
DC BIAS/AUDIO OUT
PTT HI
MON
PTT LO
AUDIO OUT (DIRECT)
GND
7
CCW
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