Option to alert employees in case of a sudden check (based on an office PBX)

Hi, Habr! Everyone knows what troubles sometimes bring sudden checks, in which it is necessary to coordinate the actions of employees. To do this, our company decided to implement a warning system.


There is:

• 3-story ordinary office
• guard post about 100 meters away from the office
• outdoor surveillance cameras

It was originally planned to install the alarm on button in the checkpoint and put calls / beacons in the cabinets. This required wiring inside the office (an extra pair of wires in the checkpoint was already, as a spare telephone line), and would also lead to unnecessary issues upon detection.
Then came the decision to make an alert based on the existing internal telephone network. The company has a PBX Panasonic TDE 200.
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Rummaging in the settings, I found the broadcast function.


This function allows you to create a conference with the maximum number of participants up to 32x, but has its drawbacks:

• the subscriber can create a conference only from a digital phone (the usual analog one is installed at the security post)
• you must wait until everyone picks up the phone at the same time to listen to the creator’s message at a time

As a result, I came up with a scheme in which a minimum of actions is enough to start the system - the button installed in the checkpoint starts the player with a repeating message, and also turns on the phone - the creator of the conference.

Old digicam KX-T7436 from the old office has long been lying idle


It remains to purchase the player, relay with double circuit, and the power supply.

From the proposed options, the relay chose HLS-14F3L-DC12V-C


The player chose a cassette, with a socket for the power supply - Sony Walkman WM-FX199


Power supply bought with switching voltage level


And for the button closing the relay used the power supply from the old switch.

All this is collected according to this scheme:


A player connected to the phone using a handset cable, at the other end connected the usual 3.5 mm jack from the headset


When assembled, it looks like this


It remains to configure the phone and PBX.

Edit and add phone numbers to the broadcast group


And on the phone set up a hot line (automatic dialing when you pick up the handset)
Enable hotline:
* – 7 – 4 – 0 – 1
Setting the broadcast number
* – 7 – 4 – 0 – 2 – * – 3 – 2 – 1 – #

Now when the button is pressed, the player and the phone are turned on (because the handset is missing, the auto-dialing of the broadcast group call is activated). The caller's phone rings and the melody plays when answered. A call forwarding to employees' mobile phones was also set up if the subscriber does not answer after a certain time.

PS: I apologize for the quality of the photos.