# What solid state components can switch composite video (AV)?

#### FuZZ1L0G1C

Mar 25, 2014
366
Our TV is quite an old model, an LG Golden-Eye CRT.
This has 2 AV inputs, one doesn't work, so let's say one AV(1) in.
One AV out.
Has RF ANT in / out.
The DSD is AV out, currently to TV's AV1 in.
The DVD/FM uses AV out (for DVD movies).
A VCR can use AV in/out or RF in/out.
The PVR is AV in/out.
The security camera is monochrome (BW) AV out, to PVR AV in, only when needed.

Currently, its a bit of a mission to dive behind the entertainment centre, into the cable jungle, to swap RCA connectors around each time I want to change the configuration.
I've been tossing some ideas around, including mini 3PDT relays, but in some switching configurations, this may short inputs to outputs, or parallel several devices, which is obviously not good.
Using logic gates/IC's, I simulated switching in Profilab Expert, and it seems that logic could work.
BUT, instead of relays, I would rather go for 3-line buffers and or switching triacs / transistors.
What device parameters would I need?
I'm thinking that maybe a minimum of 8MHz, allowing for composite video's color-burst?
Or more, to allow a margin for harmonics / rolloff?
As max V is only about 2V p-p, I guess Imax is low, probably a few mA?
As I plan to record OR playback with VCR and PVR, I am still playing around with best logic tables / configs.
As I've never used 'Arudino' or similar (Stamp), would one of these do a better job of controlling switching and direction?
An electronic component store nearby (RS) sells various micro-controller boards, so plan to shop for one.

#### kellys_eye

Jun 25, 2010
5,516
Use the KISS principle - keep it simple. The relay solution will work just fine. Proper design will prevent shorting inputs and outputs that aren't meant to be shorted.

#### Bluejets

Oct 5, 2014
6,204
One can buy a ready made av switcher for around $10......$15 with a remote for "no diving" requirements.

#### FuZZ1L0G1C

Mar 25, 2014
366
Use the KISS principle - keep it simple. The relay solution will work just fine. Proper design will prevent shorting inputs and outputs that aren't meant to be shorted.
Will re-design around relays, thanks.
One can buy a ready made av switcher for around $10......$15 with a remote for "no diving" requirements.
At our 'Hi-Fi Corporation', only seen simple HDMI multi-to-one device switching devices, will check further, thanks.

#### Bluejets

Oct 5, 2014
6,204
At our 'Hi-Fi Corporation', only seen simple HDMI multi-to-one device switching devices, will check further, thanks.
2 for relays.... Thought was at \$10 you could pop one open and see how the professionals do it.

#### WHONOES

May 20, 2017
1,215
If going the relay route, make sure they are suitable for RF. Not all are.

#### AnalogKid

Jun 10, 2015
2,702
Composit video switchers are a thing of the past, but readily available on ebay.

https://www.ebay.com/itm/804A-4-channel-CCTV-Analog-Audio-Video-Switcher-for-Security-Cameras/183315825468?hash=item2aae79833c:g:cBYAAOSw7VRbQuEN&_sop=15&_sacat=0&_nkw=security+camera+switcher&_from=R40&rt=nc&LH_TitleDesc=0|0

If you want to build from scratch, Maxim has (had?) a line of video multiplexer (mux) chips, including routing switcher chips.

The standard impedance for video signals is 75 ohms. peak current is just under 10 mA.

Video bandwidth is 4.2 MHz, rigidly controlled at the tv station transmitter with a very expensive filter. The color subcarrier signal bandwidth fits within this envelope. Security cameras and video players have no such restrictions, but most TVs cannot display a wider bandwidth signal because of limitation in the CRT.

ak

#### 73's de Edd

Aug 21, 2015
3,477
Sir FuZZ1L0G1C . . . . .

Tee Wee designers have commonly used and incorporated CMOS CD4052-4053 chips for audio and composite video switching for multi-deeeee-cades.

Check out these solid state solutions. . . . . .

73's de Edd
.....

#### AnalogKid

Jun 10, 2015
2,702
Normally I agree with 73, but not this time.

I strongly recommend *against* CD4000 series analog switches for either audio or video. The on resistance varies greatly with signal amplitude, causing harmonic distortion in audio and differential phase / differential gain distortion in color video. Also, the off-state isolation is relatively poor, especially at video frequencies. In the universe of analog switch components, these parts are a poor choice for anything requiring precision, accuracy, clarity, etc.

I did use them in an intercom system and they worked well, but for anything beyond that I'd say Maxim, Analog Devices, Linear Technology, etc.

ak

#### FuZZ1L0G1C

Mar 25, 2014
366
Fascinating and useful info, thanks.
Here in good ol' RSA, a shopping mall near us had a gadget/electronic/astro shop called 'Zoom'.
This has unfortunately either moved or ceased to exist.
They kept various types of video-based active switching consoles.
Whenever I passed them, I was a 'kid in a candy store'.
Will shop around further, or build based on advice given.

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