MODIFICATION The Monitor switch as provided is normally closed for radios 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, perform the following modification. 1. Remove the baseplate by removing the screws securing 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 terminal of the monitor switch. 4. Replace the baseplate and screws. MICROPHONE CABLES The 550T Series II can be used with various MODULINK microphone cables. Each cable has a modular microphone plug on one end and the user�s choice of equipment plugs on the other. The MODULINK Cordset Table supplied with the 550T Series II lists the most popular radios 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
MICROPHONE CONNECTOR WIRING Pin 1 2 3 4 Color NC Red Yellow Blue Function �� Bias (+), DC Audio Out PTT Switch Monitor Pin Color 5 6 7 8 Black White Drain NC Function PTT Switch Ground Audio Ground ��
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.
560 PIN 2 15 µF 9.6 VDC 1K
PIN 7
FIGURE 2 ADJUSTING OUTPUT LEVELS To adjust the output level, proceed as follows: 1. Insert a screwdriver into the sensitivity control potentiometer, located in the microphone base (see Figure 3). 2. Rotate the control counterclockwise to increase sensitivity or clockwise to decrease sensitivity.
SENSITIVITY ADJUST (CCW MAX.)
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. FIGURE 3
MODULINK CABLE RELEASE
INTERNAL CONNECTIONS The circuit board layout is shown in Figure 6 and the internal electrical connections are shown in Figure 7. A schematic diagram of the circuit board is shown in Figure 8.
