Electronic component history test

[beaky]

Hi guys.
I came across these components on a sound board for an old 1970 EM arcade game (EM game play with electronic sounds) after   I looked at the schematics and it didn't take me long to figure out what they are.
I will post the schematic for the components later but until i do lets see who knows or who can guess what 3 black things with "SIGMA" written on them are.  
 

[Olivia_jason]

 

[beaky]

a relay

Something along those sort of lines, smarty pants  

this won't last long now 

[The pinballist formally known as Dean Morgan]

Hmm, I know the answer, but only because I googled it. So I won't answer that would be cheating

[Olivia_jason]

 

[Mr Pinbologist]

Not sure what you'd call them, but my guess is that they contain an LDR (light dependent resistor) and a light bulb or LED for a light source, like an opto coupler type thing i guess  probably used to simulate a gunshot or explosion perhaps ?? 

I've seen a similar thing in old guitar amps for the tremolo circuits 

[swinks]

Cap (Capacitor) but gets too much charge and she blows. 

[beaky]

Not sure what you'd call them, but my guess is that they contain an LDR (light dependent resistor) and a light bulb or LED for a light source, like an opto coupler type thing i guess   probably used to simulate a gunshot or explosion perhaps ??  

I've seen a similar thing in old guitar amps for the tremolo circuits  

we have a winner    

well done. 6 volt lamp on one side and an LDR on the other and yes they help control the explosion sounds.

and i don't know what they are called either.    

[Pop Bumper Pete]

gum, for the tech doing late night servicing

[Olivia_jason]

 

[chris288]

I thought it could have been something like a mercury switch which cuts out if someone were to shove or tilt the machine

[Homepin]

These were used a lot in valve guitar amps for effects. I have made them up over the years using an LDR (Light Dependent Resistor) and a LED and they work a treat.

[Mr Pinbologist]

Not sure what you'd call them, but my guess is that they contain an LDR (light dependent resistor) and a light bulb or LED for a light source, like an opto coupler type thing i guess   probably used to simulate a gunshot or explosion perhaps ??  

I've seen a similar thing in old guitar amps for the tremolo circuits  

we have a winner    

well done. 6 volt lamp on one side and an LDR on the other and yes they help control the explosion sounds.

and i don't know what they are called either.    

Yay i won    whats my prize for winning  ?? 

[Mr Pinbologist]

These were used a lot in valve guitar amps for effects. I have made them up over the years using an LDR (Light Dependent Resistor) and a LED and they work a treat.

Yepp, as i said in my post above, used for tremolo in valve amps, like most Fender amps made around and after the mid 60s, though Fender and most manufacturers used a neon lamp for the light source. Some of the amps made later on also used a similar device to do the channel switching, with an LDR and a LED, same as Mike described above.

[Homepin]

These were used a lot in valve guitar amps for effects. I have made them up over the years using an LDR (Light Dependent Resistor) and a LED and they work a treat.

Yepp, as i said in my post above, used for tremolo in valve amps, like most Fender amps made around and after the mid 60s, though Fender and most manufacturers used a neon lamp for the light source. Some of the amps made later on also used a similar device to do the channel switching, with an LDR and a LED, same as Mike described above.

Yeah, sorry - I missed that part of your post......