Remote Head Enhanced - Motorola MTM800 User Manual

4.2 - 8
The Expansion PTT signal on the Telco connector is routed though the Expansion Board via Q102
and Q103. This line signals the radio that PTT is coming from the Data Expansion Head Enhanced
and the audio paths are routed through the Data Expansion Head Enhanced.
The JTAG port is provided on the back of the Expansion board. The pin layout of the connector is
setup in a way that the JTAG connector used for software debugging can be directly connected to
this port. A 14-pin m/m 90° adapter is needed to connect to the test equipment.
To select a specific configuration, pin 23 (SB9600_SW) on the 25 pin D-type connector can be used.
Also the ACC3 pin on the 12-pin flex and pin 19 on the JTAG connector influence which interface is
active in the Data Expansion Head Enhanced at a specific time.Default if nothing is connected to the
radio is that the 8-wire RS232 interface and 4-wire RS232 interface are active.
A high voltage (12V) on pin 23 enables the 8-wire RS232 interface on the 9-pin D-type connector. At
the same time the SB9600 interface on the 25-pin connector is enabled. A low voltage (0V = default)
on pin 23 enables the 8 wire RS232 interface on the 9-pin connector and the 4 wire RS232 interface
on the 25-pin connector.
If a device is connected to the accessory connector of the radio, the 8-wire RS232 interface in the
Data Expansion Head Enhanced is disabled. Also, if the JTAG port is used, a 3-Volt level is applied
to pin 19 of the JTAG, the 8-wire RS232 interface is disabled.

Remote Head Enhanced

General
The Remote Head Enhanced (PMLN4904_) and the radio are connected via 10-pin TELCO connec-
tors. A 12-pin flex connects the radio to one remote mount PCB.
Description
The remote mount board basically routes the signals necessary to drive a Enhanced Control Head
from the radio to the remote mount cable and to the Remote Mount Enhanced Control Head. The
signals (ON_OFF_CONTROL, BUS+, SCI_TX and the supply voltage) are directly routed from the
flex connector J301 to the TELCO connector J302.Microphone and speaker audio are transformed
from unbalanced to balanced by the Gabel Hybrid U202 in order to reduce noise susceptibility on
the remote cable.
The regulator U201 provides VAG_1 of 9.3V for the Gabel Hybrids U202. This regulator will be shut
down through Q101 when the 5V are detached. The supply voltage FLT_A+ is over current pro-
tected by the 2A fuse F101.
VR301 - VR304 protects the board against electrostatic discharge
THEORY OF OPERATION (ENHANCED CONTROL HEADS)