Intercom with the Panasonic F15 camera

The page describes modifying the circuitry of a camera, the risk of doing this is all yours, do not attempt this if you're not proficient at electronics.

[photo of intercom headset]
A carbon-microphone headset (1970s vintage)

Do you still use one of the 1990s-vintage Panasonic WV-F15 cameras, and want an intercom, but don't have the CCU attachments for it?  This page details how you can do that.

It's next to impossible to do a good multi-camera production without an intercom system.  At the very least you want a one-way system, so your director can instruct the cameramen what to do.  But a two-way system is better, as it allows cameraman to warn a director about something about to happen, and it vastly speeds the set-up time when technical crew can talk amongst each other.

If you had the CCUs, the appropriate WV-AD37 camera back ends, and headsets, you could use the intercom system that Panasonic designed.  The native intercom system for these cameras used a carbon-microphone and medium impedance headset, like an 1950s telephone operator's headset.  It used a ¼ inch TRS jack (tip is microphone, ring is earpiece, the sleeve common to both).  It didn't seem to matter whether a professional TRS jack is used, or an ordinary phone plug, either works just as well (over many years of use).

Alongside is a picture of one of the compatible headsets recommended by Panasonic, over the years.  This one being a 1970s-vintage headset.  It was cumbersome, never quite fitted your head properly, fell off if you looked around, was uncomfortable on the ears, and had a very crackly microphone (the boom ends with a plug going directly into a socket that's part of the microphone body).  Various other video equipment manufacturers had similar headsets, in that era.  And aircraft headsets should, also, be compatible, as they use a similar carbon-microphone, and medium impedance earphones.

The microphone power was supplied from the CCU, as well as the microphone amplifier/buffer circuitry, and another for the earphone.  The send and receive signals were kept separate, only being combined together when plugged into a mixer (several of their video mixers had compatible intercom circuitry built in), with all the CCUs intercom lines being tied together (in the mixer) for a three-wire party-line system (send, receive, and common ground).  Some of the much older Panasonic systems did it as a two-wire system, with combined audio across two wires (no separate send and receive), essentially the same as an ancient telephone system.  But thanks to the carbon microphones, and DC voltages on the connectors, it was very crackly.  And the audio was quite quiet, so the native intercom system was only suitable for use in quiet studio productions.

Without something acting as a base station, such as the vision mixer's intercom circuit, you'd have to make your own.  A versatile solution is a small audio mixer, sending an amplified microphone signal, from the director, to all the CCU intercom receive inputs (directly wired together), and then mixing all the CCU intercom talk outputs to an amplified speaker, or headphones, in the control room.  Or, a really simplistic system could send an amplified microphone signal to all the CCU intercom receive inputs, and then you'd feed the individual CCU intercom talk outputs to the camera preview monitors, and you'd use the volume controls on each preview monitor to adjust the intercoms coming back from their camera.  Or, even simpler, joining all the intercom talk outputs directly together, and connecting that to one audio monitor.

Alternatively, when you don't have the CCU equipment, you're left with using wireless headsets (very problematic), strapping a separate intercom cable to the camera lead (simple, but annoying to have to do), or modifying a multi-core cable (simple enough, and effective).

Firstly, wireless headsets:  Yet another pile of things that need batteries.  Most sets are simplex (they can only have one transmitter transmitting at a time), so there's no way to interrupt someone when you need to.  Any second person trying to transmit just messes up everyone's reception.  And you can run into interference problems with other wireless equipment.

Secondly, strapping on separate intercom wiring is simple enough, though a nuisance to set up, and makes your cabling more likely to snag on things while you move around, or more expensive if you wrape a snake around all the bundled wiring for its full length.  But it is the easiest way to add intercoms to various different bits of equipment, as being a completely independent device means that you can design it to do exactly what you want, it doesn't have to match signals with other equipment, nor fit into the limitations of their wiring.  Usually, you'll find that different pieces of equipment, that come with their own intercom circuitry, can't be directly connected together, as they each have different signal levels and operating principles.  Using an independent intercom system is the approach that we've done for many years, as it means we can bring in any cameras and use them as they are, since all we need is standard video signals from them.  And having a completely independent intercom, means that you can use the intercom while setting up the cameras.

Thirdly, modifying a multi-core camera cable.  If you have multi-core camera cables, and there is spare wiring in it (even if that means re-purposing something, such as disconnecting useless audio circuits or incompatible intercom systems, to free up some of the wiring), you can use that spare wiring for your own intercom.  For fixed set-ups, this is the neatest solution.  The simplest approach would be to simply patch the spare wiring to a headphone connector at the camera end, and plug it into a microphone amplifier at the control room end (such as using a small microphone mixer to drive several camera headphones from one, or more, microphones in the control room).  If all you need is a one-way system, this is probably the easiest and best way to do it, the cameras only need ordinary cheap headphones, and they can be easily replaced if damaged.  We've done this with one system, when we modified the back end to add line view to an installation without any CCUs.  But if you need a two-way system, there's a few ways that you can do that:

If you have enough spare wires in your multi-core, you can patch a microphone lead back to the control room, and use another mixer to mix together all the camera operator microphones, for the control room crew to hear the floor crew through headphones or a loudspeaker.  This gives you the basic two-way intercom system, similar to the way many professional systems work (separate sends and receives to each camera, and no need to wear headsets in the control room).

As a bit of an improvement, you can pre-amplify the camera operator microphone at the camera end, and send a higher level signal back to the control room mixer.  This would minimise any hum you might, otherwise, have had to put with from long microphone leads.  And means you don't need a microphone mixer in the control room to hear the camera talkback.  At one stage, we plugged camera intercom return feeds into the camera preview monitors' audio inputs.  That avoided the need for mixing, or separate amplification, and gave us individual volume control for each camera operator—the sound came from a logical place, and was easy for anybody to understand how to adjust.  There's enough space in the camera back ends to fit a small microphone amplifier, and you could easily tap off 12 volts from the camera power, to power it.  Though, if you used a separate wire for sending to the camera, you can take intercom audio from the camera's own microphone pre-amp, without needing to modify anything.

Or you can make a two-wire party line intercom system.  You'd fit a microphone and headphone amplifier in each back end, where the microphone is amplified and fed to its own headphones.  The point between the microphone and headphone amplifier is connected to the intercom line, and joined to all the other intercom stations in the same way (each of them are joined at this mid-way point), for all the cameras, and stations in the control room.  This gives you a simple to operate system, where everyone can talk together.  Though, if you want to use a desk mike and loudspeaker, rather than require the control room crew to wear headphones, it needs careful design of the control room stations, to null out their own microphone.

Some people will refute the idea of needing two-way intercom, or allowing floor crew to be able to talk back during a production, but I've found it more than useful for camera operators to be able to say when they're about to run out of cable, or pass some other message along, especially when a problem occurs that you could either fix now, or have it mess up the rest of your production.  It's a godsend for live productions, where you can't stop and talk through a problem, you need to be able to talk, both ways, to fix something while still producing.  And it's virtually essential for the setting up of temporary equipment when you're out on location.  It's better to train the crew to not talk unless needed, rather than make it impossible for them to talk back.

Though for small studio productions, where you're not doing live television, it's easy enough to get away with a one-way intercom.  The director speaks into a desk microphone, it's amplified and sent to headphones at the cameras.  In between recordings, the floor crew can talk back to the director simply by raising their voice so they can be heard through the boom microphone that'd normally be used for recording audio.

So what do we do?

Since we use various different cameras, not always the same ones, not always our own (so we can't customise them), and usually stand-alone cameras without CCUs, we built up custom multi-core camera cables.

There's an ordinary mains lead, to power the camera from a local supply (running 12 volts DC up 50 metres of cable doesn't always work very well).  And not everything runs off 12 volts, anyway.  Wrapped up with the power lead is a generic multi-core video lead, that plugs into breakout boxes at each end.

Rather than use a multi-pin connector that would only ever suit one model of camera, we plug into generic breakout boxes with a couple of BNCs for video lines, and other jacks for tally lights, and intercom.  Short patch leads are used between the breakout box and the camera head, likewise at the control room end (patch leads between the box and mixing equipment).  That gives us quick connections, and cabling that will work with any equipment.

The camera end of the cable has the intercom built into the breakout box, to avoid having a cluster of boxes at the camera.  Though it could be more convenient to separate the intercom into a satellite box, and strap it to the tripod arm (putting volume controls and mute switches nearer the cameraman's reach), it can make balancing the camera harder, and cause the cameraman to wobble a live shot while fiddling with the controls.  Likewise, intercom controls mounted on the back of the camera can be a cause for wobbling a shot during adjustment.  We found it more practical to mount the box below the tripod head, although that means camera operators must not turn the pan/tilt head around and around.  But they already had that restriction, thanks to there being a power supply box strapped to the tripod base.

We went the extra mile with our custom intercom system, and added in a second audio line.  Which could be used for technical crew to talk to camera crew without disturbing the director, or for the camera crew to be able to hear the program sound.  The latter being essential for crew to be able to manage shots that are dependent on the program content (they mightn't be able to hear talent directly, or the program might use sound coming from somewhere else).


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