Installation Guide

120 20110-142 Gemini
PD
Installation Guide
24
Appendix 1 - "Officer Requires Assistance" alarm function
The contents of this appendix are also available as Technical Instruction Sheet 009 (TIS009),
document part number 122 20110-009 dated December 20, 2000.
Overview
The DTE Port Interface pin 9 (AUX) on DEV-2 is used for the
“Officer Requires Assistance”
alarm function.
Intended Audience
This document is designed for use by System Integrators.
Physical Connection
This auxiliary input may be activated by (normally open) dry contact pull-up to the port’s DSR
output. It can also tolerate user pull-up to external +12 VDC (car battery), but an isolated dry
contact is preferred due to the risk of noise-related false alarms caused by the vehicle’s electrical
system.
A +3 to +12 V signal at this pin will send a DMP
“x”
(On) message to the base.
An open or ground signal will send a DMP
“y”
(Off) message.
Messages are only sent when a signal transition occurs (debounced for approximately 100 ms).
Operation
When using Gemini
PD
or Gemini
PD
Lite products, activating the
“Officer Requires Assistance”
alarm input starts emergency communications:
• The modem creates DMP
“x”
or
“y”
messages.
• Any other pending message(s) will be failed to avoid delaying the alarm message on account
of lower priority traffic and to remove non-emergency messages from duty-cycle management
(if applicable). In the case of a “q” message, a D-NAK* will be immediately returned.
• Base and Channel hunt will take place for the usual number of retries per base (according to
configuration) but will cycle forever until D-ACKed* or Reset*.
• Lack of base DBA synch will not prevent transmission to maximize the chance that a base
gets the alarm signal. DBA “Freewheel” mode will be forced until the alarm is acknowledged.
* For details on DMP terms, refer to DMP 1.5 manual, version 4.0