Door phone bell but what produces the sound?

[Barrymore]

I have a Kocom door phone with the bell switch wired from the gate to the phone in the house.
It has stopped working and naturally I first checked the wiring but found no fault. 6v DC reaches the phone inputs.
I opened up the unit and while I found nothing untoward, I am left wondering what produces the bell sound as there is only a circuit board with no speaker. It someone could enlighten me I can then decide whether I need to buy another unit.

 

[HibiscusTunes]

Do you have a picture? Sometimes the buzzer is in the plastic case, and is connected to the circuit board by springy connectors.

 

[gregmcc]

Could be a small piezo buzzer. Post pics of the PCB

 

[Barrymore]

Ok, I learnt that the board has a electromagnetic field which somehow produces the sound.
I bridged across the two wire contacts and it worked. I then followed the wires about 40 meters down to the
gate and checked each point where the wires had been joined, touching them together to get the bell to work,
but nothing. Eventually at a point about 10 meters from the phone joining the wires worked, but for some strange reason
just a meter further on it does not work. Very strange, as that extra meter has no joints that could have rusted over time.

 

[TheChamp]

Ok, I learnt that the board has a electromagnetic field which somehow produces the sound.
I bridged across the two wire contacts and it worked. I then followed the wires about 40 meters down to the
gate and checked each point where the wires had been joined, touching them together to get the bell to work,
but nothing. Eventually at a point about 10 meters from the phone joining the wires worked, but for some strange reason
just a meter further on it does not work. Very strange, as that extra meter has no joints that could have rusted over time.

The wires can get disconnected from inside the insulation which won't be visible to the eye as the insulation will still be in place, the only good way to test for continuity is to use a multimeter.

Your troubleshooting is good though, it means there is a disconnection from the point when you can't get the buzzer to sound.

Lastly there should be a better explanation than this:

Ok, I learnt that the board has a electromagnetic field which somehow produces the sound.

 

[Barrymore]

The wires can get disconnected from inside the insulation which won't be visible to the eye as the insulation will still be in place, the only good way to test for continuity is to use a multimeter.

Your troubleshooting is good though, it means there is a disconnection from the point when you can't get the buzzer to sound.

Lastly there should be a better explanation that this:

You were right. A multimeter confirmed that one wire was broken inside the insulation.