E.F. Johnson Company 5100 ES, Service Manual

Page: 32 / 180

2-4 5100 ES Series Portable Radio Service Manual January 2007
Battery, Accessory and Disassembly Information
Figure 2.3 Accessory Installation
2.3.1 Option Select Lines
Opt Sel 1 (pin 1) and Opt Sel 2 (pin 5) of the UDC (accessory) connector indicate to the
control logic when an accessory is connected and what accessory is installed. These lines
function as follows:
Opt Sel 1 and 2 High (3.3V) - This is the normal operating condition in which no
accessory is connected. Both lines are pulled high (3.3V) by internal pull-up resistors.
Opt Sel 1 Low - A speaker-microphone or some other accessory is connected. Opt Sel 2
then functions as an external PTT line (low = PTT), and the radio PTT switch is also
functional. The internal speaker and microphone are disabled.
Opt Sel 1 High, Opt Sel 2 Low - The encryption keyloader is connected.
Latch
Install Lock
Screw Here
Accessory Connector
Hook