Carrier Operated Light, Multiple Scanners

[N9JIG]

Several years ago Bob Parnass, AJ9S, wrote an article detailing the installation of a Carrier Operated Light (COL) on the Radio Shack PRO200x scanners.

I would like to install COL's on a series of scanners at my office, including the following models:

BCD996T
BC15
BC796
BC785
BC780
BC796
Pro2096

Is there anyone who has installed COLs on more recent scanners that wishes to impart the knowledge?

 

[jonny290]

Download schematics, find a line that goes high when there's carrier - all CPUs should have such a pin, build a buffered OR gate with an LED driver transistor on the output. Should do ya okay.

 

[902]

Several years ago Bob Parnass, AJ9S, wrote an article detailing the installation of a Carrier Operated Light (COL) on the Radio Shack PRO200x scanners.

Is there anyone who has installed COLs on more recent scanners that wishes to impart the knowledge?

I haven't done exactly that, but I have had to extract carrier detect logic from various things. LEDs are more or less similar to the devices I've interfaced.

It's not hard to do if you have messed around with electronics, have an oscilloscope or access to a detailed service manual. This is very general - On a frequency with regular activity, probe the lines from the microprocessor to find one whose voltage corresponds to the presence of received signal. The detailed service manual can sometimes tell you exactly where that is, or at least point you toward possible tie points. DANGER! For a number of reasons, you may short something. Please don't hold me responsible if you have confidence in your abilities but end up smoking the thing.

A transistor should be able to pass current to an LED without loading down the line. I would put a 10K resistor in series with the base of the transistor.

Good luck and don't do it if you need more specific instructions.

 

[iMONITOR]

Maybe he'd share his ideas with you!

Robert S. Parnass, MS

http://parnass.com/

bob@parnass.com

 

[K8PBX]

Maybe consider using LED VU meters?

CanaKit has some pretty cool ones that can be ordered in kit form or assembled. LINK HERE

 

[DaveIN]

I think you could do it on the list of radios you have, but the new GRE PSR-500 and 600 are listing this feature (and many others). I can see it being real useful.

Audible Alarms and the ALERT LED
Your 0715 features a very powerful ALERT LED with Audible
Alarm capability that allows you to set different types of visual
and audible notifications for the different types of objects you
create.
You may have noticed that the menus for each object you create
include various settings for LED, Backlight and Alarm. You can
use these settings to design custom visual and/or audible alarms
that are triggered when activity is detected on the specified
Scannable Object.
Audible Alarm and ALERT LED Settings""
Each object you create has the following ALERT LED and
Audible Alarm settings:
LED Mode: Solid or Flash controls whether the LED
remains on solid or flashes when the object is active.
LED Color: 0-7 sets the color of the LED. By default, color 0
is used for LED off. You can change the LED colors in the Global
Settings menu.
Latch LED keeps the LED on after activity on the object is
finished. This is useful in cases where you need to know if an
object was active while you were away from the scanner.
Backlight: Off, On, Flash controls whether the backlight
remains off, comes on solid or flashes when the object is active.
Alarm: None, Chirp, Hi-Lo, Alert, Ring, 2-
Chirp, Fast Hi-Lo, DTMF # are used to set audible
alarms that play each time activity is found on the object.
ALERT LED with Audible Alarm Examples
Here are some examples of when you may wish to use the
ALERT LED with Audible Alarm capability:
• You have programmed a Talkgroup Wildcard in for a trunked
radio system you monitor in order to find new talkgroups. You
can use an Audible Alarm to alert you when the radio receives
a wildcard hit, and turn on the backlight so that you can read
the display and operate the keypad to save or lock out the new
talkgroup.
0715 User Manual" Page 47
• You have programmed you favorite amateur radio repeater in
and wish to be alerted when a QSO begins. You can use an
Audible Alarm with one of the shorter alarms (Chirp, 2-Chirp,
Fast Hi-Lo or DTMF #) to provide this indication without
covering the traffic in the QSO.
• You have included a Spectrum Sweeper object in your scan
configuration so that you can find nearby strong transmitters
while you are scanning. You can use an Audible Alarm to alert
you when the radio receives a Spectrum Sweeper hit, and turn
on the backlight so that you can read the display and operate
the keypad to save or lock out the new frequency. This
technique is also useful for TGRP wildcards.
• You wish to assign different LED colors to different types of
public safety agencies, i.e., red for fire, rescue and EMS, blue
for law enforcement, yellow for emergency management, and
so on. When there is activity you can tell if it is related to law
enforcement, fire/rescue and EMS or emergency management
at a glance, even if the transmission is short or difficult to copy.
The possibilities for the ALERT LED with Audible Alarm capability
are limited only by your imagination.

 

[bctrl1]

Although designed with the 898t in mind, the circuit described in the PDF below provides this function for the 780, 898, and most likely the 785 and 796.

http://www.bearcontrol.com/DOCS/LineXtrl_AutoLight.pdf

 

[slicerwizard]

I would like to install COL's on a series of scanners at my office

I doubt that you really want carrier controlled backlights, since a carrier is always present when monitoring most trunking systems. Rather, you want backlights that operate in sync with a scanner's audio unmute function.

These days, most scanners use audio amplifier IC's that have a mute/unmute input pin. That pin is directly controlled by one of the micro's I/O lines. The audio IC's are easy to spot (you can just trace back from the earphone jack) and datasheets are available for all of them; that gets you the control pin for your mod. Hell, even without a datasheet, you can just use a voltmeter to find the right pin.

I assume you want to use the existing LED backlighting; it's generally controlled by a single transistor which is driven by another I/O line from the micro. That means that the conversion may involve nothing more than moving that transistor's base circuit connection to the audio IC's mute/unmute pin. You can find the transistor by tracing back from the LED's.

If the logic levels are wrong (e.g. a direct connection would turn the backlight on when audio is muted), a single transistor can be added to invert the control signal.

Anyone with a bit of electronics skill should be able to run with that. If that's not you, you'll have to find someone.

 

[frankh]

check Bill Cheek's Scanner modification 2, article on squelch operated cor that may help, or here's a plug 'n' play solution http://www.ncsradio.com/m_rx.html.

 

[N9JIG]

I doubt that you really want carrier controlled backlights, since a carrier is always present when monitoring most trunking systems. Rather, you want backlights that operate in sync with a scanner's audio unmute function.

Right, I never said I wanted a carrier activated backlight, that was someone else in the thread. I just want a simple LED that lights up when the carrier is active. I really don't need it for trunked systems so I don't care if it comes on during idle time on a control channel.

Basically in my case I want to see which of my half dozen BC15's is active with a Fire Tone Out call or which of my BC780's/785's or 796's is active with voice traffic for various fire, air or "second radio in Trunker/Pro96Com/Unitrunker" is squawking.

 

[slicerwizard]

Well, that certainly simplifies things. Pick a scanner and crack it open. You shouldn't have much trouble finding the audio amp or the pin that switches between high and low as the audio mutes and unmutes. Use that point to drive a transistor to switch the LED on and off. Total parts per scanner: one LED, one transistor and one or two resistors.