Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; WpFlickrEmbed has a deprecated constructor in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/plugins/wp-flickr-embed/wp-flickr-embed.php on line 34

Warning: session_start(): Cannot start session when headers already sent in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/plugins/wp-flickr-embed/include/class.flickr.php on line 104

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Suffusion_Widgets has a deprecated constructor in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/themes/suffusion/widgets/suffusion-widgets.php on line 10

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Suffusion_Search has a deprecated constructor in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/themes/suffusion/widgets/suffusion-search.php on line 9

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Suffusion_Follow_Twitter has a deprecated constructor in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/themes/suffusion/widgets/suffusion-twitter.php on line 10

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Suffusion_Category_Posts has a deprecated constructor in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/themes/suffusion/widgets/suffusion-query-posts.php on line 10

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Suffusion_Featured_Posts has a deprecated constructor in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/themes/suffusion/widgets/suffusion-featured-posts.php on line 10

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Suffusion_Google_Translator has a deprecated constructor in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/themes/suffusion/widgets/suffusion-translator.php on line 10

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Suffusion_Subscription has a deprecated constructor in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/themes/suffusion/widgets/suffusion-subscription.php on line 20

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Suffusion_Flickr has a deprecated constructor in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/themes/suffusion/widgets/suffusion-flickr.php on line 10

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Suffusion_Query_Users has a deprecated constructor in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/themes/suffusion/widgets/suffusion-query-users.php on line 10

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Suffusion_Child_Pages has a deprecated constructor in /homepages/42/d24067567/htdocs/clickandbuilds/WordPress/rtn_vfrmedia_newblog/wp-content/themes/suffusion/widgets/suffusion-child-pages.php on line 10
January 2015 – rtn VFRmedia
Jan 272015
 

I want some bright lights to flash in the studio when the VFR extension rings (rather than bells sound). The analogue telephone circuit uses a ringing signal of 80-90V AC at 25 Hz (it is quite strong; if you accidentally hold on to bare telephone wires it can definitely be felt!) – and all sorts of random signals can come down a phone line.

So I had to build a circuit to isolate the phone line from any other equipment; not let through any DC electricity (or the phone line will be permanently engaged) and reduce the voltage from the line to trigger an optoisolator.

first video is internal PABX call

second is external call

the circuit is here – the zeners are 10V and capacitor (to block DC and not seize the phone line) 470nF.

The PNP transistor switch is used as the opto is connecting to ground – the 10K resistor which also acts as a check for the opto output (as those 6 LEDs will eventually be in another unit elsewhere) also is a pull-up resistor for the transistor switch. The LED LD1 still glows very dimly even when the circuit isn’t active; maybe I should remove the 220K resistor (that was recommended in the original transistor switch design) as there is actually only 18k resistance between the 12V supply and the “active” LED and possibly leakage current gets through.

That said TBH it works and provides the signals I want so I may leave it at that…

 

telephone ringing detector + LED driver cct