Friday, November 20, 2020

Please help with a simple audio amplifier design

Hi, I’m trying to make a little intercom thing so that a guy on one side of a glass barrier can talk to a guy on the other side. Commercial solutions are really pricey and I can’t afford any of them but I figured that I could probably make one by replacing the guts of a Kocom outdoor station with a regular amplifier. My soldering skills are ok, but my knowledge of audio electronics is weak. I just want to take the little microphone in one Kocom DS-2D and wire it through an amplification circuit to the speaker in the other Kocom DS-2D and vice versa so that the guys on either side of the glass can hear one another speak. The speakers are 8 ohm 0.5W but I have no information on the microphone.

I’ve tried using these https://mantech.co.za/ProductInfo.aspx?Item=15M6431 but they don’t work.

I then tried using a velleman preamp kit (can’t find the link now) wired up to one of those and it didn’t work so I then tried the velleman preamp wired up to one of these https://www.communica.co.za/products/kemo-m031n

To be clear, by doesn’t work, I mean that I have to put my mouth onto the microphone and make noise for any audio to come out of the speaker. That is for all configurations.

I've gotten to the point that I've given up with kits and will make my own circuits on veroboard but I don't know what design to go with - the internet has a bunch of different ones but I don't know if they would suit my purpose. I'm leaning towards using this (http://archive.communica.co.za/Content/Catalog/Documents/D0793670597.pdf) as a basis but not having the switch to select talk or listen.

Can someone help?

Thursday, November 5, 2020

TS is in JPAS archive (I retired 23Jun) and ManTech is talking about making it active with an SCI

I have applied to a job in CA for ManTech that requires TS with SCI. I have had a TS for years but never had an SCI. I retired in June so the hiring manager told me my clearance has been archived in JPAS. So they would need to bring it out of the archive and get an SCI.

Is that a long process? What should I expect?

TIA!!!