Bell Box FAQ2015-02-04T14:59:11+00:00

A selection of Frequently Asked Questions relating to our Bell Boxes. Click on the questions to find the answers.

My Inca / Protecta Sounder is constantly emitting a bleeping noise. What's going on?

The universal assembled sounder will do this if the 1K ohm resistor is missing across the bell terminals in the control panel or if the cable is damaged

What is TWM (Trigger Wire Monitoring)?

Trigger Wire Monitoring is the CQR method of additional protection to the bell and strobe wire connections. CQR have utilised this technology for commercial sounders for many years with great success. Due to forthcoming legislation CQR have now implemented this technology on all their Security Grade 3 sounders. Existing sounders have this as a built in feature. New sounders will have this as a selectable option. Traditionally, sounders would only operate if the integrity of the bell and strobe outputs remained functional at the sounder. If the integrity of those connections failed up to the point of the sounder then the sounder could fail to operate. The use of two shunt resistors to provide a monitoring current on the bell and strobe output of the control panel simply monitors the connection integrity.

On the xxxxxx sounder am I required to fit the resistors?

The xxxxxx sounder has a TWM (Trigger Wire Monitoring) in order to comply with the EN50131–4 Security Grade 3. This requires the use of two 1k resistors IN the CONTROL PANEL. The xxxxxx sounder can monitor the current at the terminal inputs to check for interconnection integrity. The resistors act as a shunt to prevent a short circuit at the control panel.

How does TWM (Trigger Wire Monitoring) work?

Normally when the control panel is not in alarm mode there is no current flowing along the siren or strobe cable. If the cable is cut then no alarm is generated. When two resistors are added between the Hold Off supply and the sounder inputs a small current is then present on the trigger wires. The sounder monitors this current. If the current is not present due to cut cable or shorted out connections then an alarm signal is generated

Does TWM (Trigger Wire Monitoring) work with my control panel?

There should not be any compatibility problems because TWM does not interfere with the normal operation of the control panel. TWM only uses two 1K resistors to place a small current on the bell and strobe wire when they are not in use by the control panel. Control panels generating alarm conditions effectively shunt out the TWM feature in alarm mode and continue to function correctly. TWM is returned when the alarm condition has finished. There are no adverse effects from using TWM.

How do I connect the two 1k resistors?

It really is a simple procedure. Done once and it can be done a million times over. Wire the bell to the panel as normal but do not connect the Hold Off supply at the bell until last. Make sure that the resistors have been placed in the control panel before the hold off supply has been applied (this is because the sounder looks for a current from the resistors when the sounder is initially powered).

1. Connect all panel connections for the external sounder and fit resistors across terminals in control panel (see FAQ 5.).
2.At the sounder connect all sounder connections but leave Hold Off + until last.
3. Connect Hold Off + and the SAB battery. The unit will bleep and one LED will illuminate to indicate it has powered up.
4. Close Lid. The unit will give a second bleep and a second LED will illuminate to indicate that the tamper mechanism is functional.
5.The unit will emit a third bleep and a slow alternate flash will be indicated from the LEDs. This is a five minute test mode suitable for sounder and strobe testing.
6.The unit will emit a fourth and final bleep and the LEDs will speed up to a normal alternating flash rate to indicate that the system is in normal working mode

What terminals do the resistors need to connect to?

The resistors need to supply the opposite voltage to that of the bell output trigger voltage from the control panel when the system is in alarm condition. So if a negative applied voltage is used to trigger the sounder then the resistors need to connect the bell and strobe outputs via the resistors to a permanent positive supply. If a positive applied voltage is used to trigger the sounder then the resistors need to connect the bell and strobe outputs via the resistors to a permanent negative supply.

When do I not need resistors?

Some control panels that have a reverse output polarity do not require resistors (essentially the resistors are built in to the panel).