Technicolor - Thomson Electronic Accessory Gecko Frames Signal Processing System ユーザーズマニュアル

Refer to 

 for an example of a typical alarm schematic using pins 8 

and 9 of the RS-232 port.

The impedance between the pins 8 and 9 of the RS-232 connector can be in 
one of two states:

•

Open – less than 100 µA of current will flow with 5 volts across the pins, 
and

•

Closed – less than 0.2 V will appear from pin 8 to pin 9 with 20 mA of 
current flowing.

There are three operational conditions (capability is module dependent, 
refer to specific module instruction manual):

•

Open – no faults,

•

Closed – there is an internal fault, and

•

Pulsing – there is a missing or invalid signal on one or more of the mod-
ules.

+5V

4.7 k

Ω

4.7 k

Ω

330 

Ω

470 

Ω

Alarm
LED

2N4126
(or equivalent)

RS-232 Pin 8

RS-232 Pin 9