# Intercom System on a budget



## Christopher Haws (Oct 31, 2017)

Hello,

I volunteer at a few local High Schools who don't have huge budgets for purchasing equipment. For the past several years we have been using 2 way radios for communicating between sound, lighting, stage management, and our spotlight. The biggest issue we have is that 2-way radios are only half-duplex so only one person can talk at a time. This gets pretty annoying when we are trying to cue each other for entrances. exits, etc.

One of the schools in our district has a built in clear-com system which is a luxury to use. I have been looking into purchasing a system for our school that would hopefully function similar to theirs. After looking for several days, I have come to the conclusion that these systems are _expensive_! Since we really just don't have the budget, I am looking for a cheaper alternative.

Here are some unconventional solutions I came up with that are within our budget:

*Lineapp Flux Smartphone App:*
Pros:
- Full-duplex intercom
- Works on iOS and Android so all of our students can use it
- Fairly cheap (3 euro's per device per day)
- Supports groups so the stage manager can communicate with different groups or all groups
- Works over LAN, no need for an internet connection
- Works with any smartphone headset
- Works even when the app isn't open and when the smartphone is locked which saves a lot of battery
Cons:
- We don't like the per device per day licensing model. We would rather pay one time since getting approval with the school can take time
- Requires everyone to be connected to the same network
- WiFi's range isn't amazing, so there could be range issues
- Battery life could be an issue with smartphones
- Small latency (around 20ms). This wont be an issue for us, but could be for others

*Self-Hosted Mumble Server:*
Pros:
- Free
- Works on iOS and Android so all of our students can use it
- Works over LAN, no need for an internet connection
- Full-duplex (everyone can be talking at the same time)
Cons:
- Requires a computer to be hosting the server
- Requires everyone to be connected to the same network
- WiFi's range isn't amazing, so there could be range issues
- The push-to-talk feature in the app requires you to press a soft key in the app (cant use the button on the headset to talk)
- Without the PTT feature, everyone's mic is always hot unless you purchase headsets with an inline mute switch
- Small latency (around 20ms). This wont be an issue for us, but could be for others

*2 Way Radios:*
Pros:
- Pretty cheap (can get 8 radios for around $100)
- Long range
- Multiple channels
- No noticeable latency
- Decent battery life
Cons:
- Half-duplex communication is a real pain
- Anyone with a walkie talkie can interfere with our show


As a last note, can anyone explain from a technology perspective why intercom systems are so expensive? Is this simply a supply and demand problem or is there a technology reason for this? I am a software developer by day, so if you can throw me a technical answer I would really appreciate it!


Thanks!
Chris


----------



## MNicolai (Oct 31, 2017)

Look at Listen Tech's ListenTALK lineup. It's intended for tour guide groups but it's full-duplex, programmable if you need multiple channels, PTT, low (no?) latency, rechargeable, etc.

Otherwise look at baby monitors.

Cheap 2-way radios are usually more trouble than they're worth, low-quality, and half-duplex. The various smartphone apps have too much latency, are contingent upon having decent WiFi coverage, and really aren't viable for anything mission-critical. Not to say there aren't people who have made this work for them, but it's not without complications and limitations. Plus if you're always stumbling around backstage with your phone in your hand there's an increased chance of a regrettable stumble.


----------



## Christopher Haws (Oct 31, 2017)

Hi MNicolai,

Thanks for your response. The ListenTalk lineup starts around $1000 which is out of our price range, however if we ever get money I will definitely look into their products. I can see the school justifying a few hundred dollars, maybe even up to $500, but I just don't see them spending more than this. I realize that beggers can't be choosers, which is why I am willing to sacrifice range and latency for price.

Our theater is not huge (only seats around 300 people) so range is not a huge issue for us. The different apps I have tested all have a latency around 20ms to 30ms which I am willing to accept. As for holding smartphones, this shouldn't be an issue since we would purchase headsets like these which have a push to talk button inline on the cable: https://www.amazon.com/dp/B01KFLGKB6/?tag=controlbooth-20

I realize that this is a pretty jimmy rigged system, but we just don't have the money for an expensive system, otherwise I would get one in a heartbeat! 

Is there a reason full-duplex systems are so expensive?


----------



## josh88 (Oct 31, 2017)

Like Mike mentioned, you could look into baby monitors, there's an app called Zello that my students have used.


----------



## Amiers (Oct 31, 2017)

Consistency is the main reason. You buy the knowing that it will work each time you pick it up. 

Mumble is a good app to use. Apple Ear buds is my goto with the inline mute.


----------



## MNicolai (Oct 31, 2017)

You can also look at Eartec's products. I've seen them mentioned around here a few times before but haven't used them myself. 

 Eartec UL3S UltraLITE 3-Person Headset System with Batteries, Charger & Case (Single) 

The wireless production intercom products usually are a cost premium because they _have_ to work. Mission-critical. Usually very specific feature requirements too for the target markets. We're not talking about "oopsie I was late on a cue so subtle only the designer would notice" mission-critical. I'm talking about "something in the truss just caught fire we need someone to scuttle up right away" or "Standby for actor to clear out of way to begin lowering the 900 lbs unit on-stage. Actor ....pfft.pfft.fpfttpf.....GOGOGOGO"

It's all a matter of perspective. The average, non-special, uninteresting vocal mic that requires no firmware, software, or 18 months of research and development is $100. A wireless, almost-as-reliable, almost-as-good-sounding equivalent is $2000 per wireless mic system system. You'll find that most of the people who found $600 wireless mic systems are the same people who've had to replace their systems twice in 10 years because of FCC spectrum auctions, and they can only operate X number of systems simultaneously. $500 or $1000 just doesn't go that far for professional grade equipment. The 8 radios you can get for $100 might as well be a scam. I've owned a few myself over the years and they almost never live up to the marketing specs and half the time you cannot understand what the person on the other end is saying even if they're standing in the same room as you.


I'm sure there are more technical explanations out there about why the market is the way it is, but this is where we are.


----------



## JohnD (Oct 31, 2017)

I have no idea if this would even be worth the effort, but considering the large number of production companies there it might be worth contacting them to see if in some dark corner of their warehouse they have some old Clearcom. They could donate to the school and get a tax deduction. 

Now for the rambling old geezer part: Does anyone else remember the early intercom which consisted of Western Electric #52 headsets, a battery (6 volt lantern battery with screw terminals IIRC) and a wire, yep they were wired in a series loop.


----------



## RonHebbard (Oct 31, 2017)

JohnD said:


> I have no idea if this would even be worth the effort, but considering the large number of production companies there it might be worth contacting them to see if in some dark corner of their warehouse they have some old Clearcom. They could donate to the school and get a tax deduction.
> 
> Now for the *rambling old geezer* part: Does anyone else remember the early intercom which consisted of Western Electric #52 headsets, a battery (6 volt lantern battery with screw terminals IIRC) and a wire, yep they were wired in a series loop.


@JohnD And when the granules in your carbon mics began to fuse together, you unplugged your mic and beat the heck out of it to free up the granules for another week or two. Don't forget the dual mono phone plugs with the mic wired across the two tips and the earphone wired across the two rings so you could mate them either way around with zero problems. Those manufacturers thought things through pretty carefully in the glory days. 
*EDIT*: I omitted an 'r' in 'your'. 
Toodleoo!
Ron Hebbard.


----------



## microstar (Oct 31, 2017)

JohnD said:


> I have no idea if this would even be worth the effort, but considering the large number of production companies there it might be worth contacting them to see if in some dark corner of their warehouse they have some old Clearcom. They could donate to the school and get a tax deduction.
> 
> Now for the rambling old geezer part: Does anyone else remember the early intercom which consisted of Western Electric #52 headsets, a battery (6 volt lantern battery with screw terminals IIRC) and a wire, yep they were wired in a series loop.



I think I still have a few impressions in my skull from those carbon mic headsets. They did work though and were pretty rugged to boot.
I've also used a system that had standard headsets with all the dynamic mics paralleled across a Bogen PA amp's mic input and all the headphones wired across the amp's output with a series resistor to keep the impedance from going too low. Actually worked pretty well even with varying numbers of headsets. Had no control over individual volume levels, just input and output adjustment at the amp.


----------



## RonHebbard (Nov 1, 2017)

microstar said:


> I think I still have a few impressions in my skull from those carbon mic headsets. They did work though and were pretty rugged to boot.
> I've also used a system that had standard headsets with all the dynamic mics paralleled across a Bogen PA amp's mic input and all the headphones wired across the amp's output with a series resistor to keep the impedance from going too low. Actually worked pretty well even with varying numbers of headsets. Had no control over individual volume levels, just input and output adjustment at the amp.


@microstar @JohnD When I first took over sound in the Stratford Shakespearean Festival's main stage, I was initially puzzled by how the mics were wired on their monitor / page system. Similar to what you're describing, all of the PTT (Push To Talk) paging mics came up on one mic input. All over the building, they never unplugged mics when they had no need of them. If a rehearsal hall was being pressed into service for pre-show exercises and warm-ups, the paging mic would simply be set on the floor below the SM's table and left plugged in. Eventually I learned why. All of the dynamic, low impedance, balanced mics were wired in series into a single microphone level input. NOT parallel, SERIES. When none of the mics were activated, the mic input was effectively shorted out by all of the NC (Normally Closed) PTT (Push To Talk) switches. Whenever any one mic was activated, its normally closed switch would be opened thus inserting the low impedance dynamic mic element in series with all of its shorted out / bypassed siblings. All of this terribly unbalanced mic level wiring running around three elevations of the Festival's original main stage / thrust building. Eventually I rewired the system such that the seven mics came up as seven inputs on a cascaded pair of Shure M67 and M68 mic mixers feeding into a Shure M63 filter unit providing a balanced +4 output with a tasteful little VU meter to drive into a line level input on the ElectroVox 70 volt monitor page amplifiers. 
Pre my Stratford days and pre ClearCom, Hamilton, Ontario`s 2,183 seat soft-seater was using a Shure M68 in the same fashion as Microstar`s Bogen with several zones of dynamic headset mics paralleled into the various balanced mic inputs and the lone low impedance balanced output driving every dynamic headphone in the place. The poor over worked little M68 kept right on working in spite of the abuse for several years until ClearCom came along.
Toodleoo!
Ron Hebbard.


----------



## JonCarter (Nov 1, 2017)

[QUOTE="Now for the rambling old geezer part: Does anyone else remember the early intercom which consisted of Western Electric #52 headsets, a battery (6 volt lantern battery with screw terminals IIRC) and a wire, yep they were wired in a series loop.[/QUOTE]

Yes, remember them very well. Tried the series circuit but gave it up fast for a talking circuit out of an old (300-series) WE phone. Put a dozen stations in parallel and give it 16V of well-filtered DC and we were in business. I may still have a few stations hanging around in a box somewhere.


----------



## AudioGreg (Nov 5, 2017)

we have used mumble with great success, but have since moved over to an app called "intercom for android". There is an IOS version as well. Works very similar to mumble tho, but does not require a server. This app is def worth a look.

to extend wifi range, we have connected 2 or more wifi points (routers or just plain AP) together with cat5 or fiber. one on the stage, another in the control room usually covers all of our space.

there are many android phones on the pre-paid shelf at Wally/Target that can be had for as little as $25. cricket makes a really nice one. you don't have to activate the phone for service, just connect the wifi, install the intercom app and go. cheap headsets can be found for the phones for as little as $10. the app supports inline switch to toggle h/s mic on-off, as well as a hardware key on the phone if present. BT h/s also supported. There are some BT PTT switches I have seen, but not tried them yet for functionality.

battery life-we have run the phones for 2 or more days of production before needing to charge.

for bonus points, we have connected a phone handset into a wired RTS system, great pair up!


----------



## EdSavoie (Nov 5, 2017)

Mumble is really nice because it is free and can be configured to a low latency. It does have the disadvantage of needing to host a server (I use server loosely, it'll run on almost anything)

Alternatively, Discord (also free) is proving to be a valid choice. Similar if not less latency than mumble, no need to host your own server, and the app of course has text chat, small file transfer, and now video calls on top of that. The only major con to it I can think of is that you are relying on discord's servers for most of the text functionality, but i'd trust a datacentre over the computer stuffed in the back room from 2005.


----------



## ProFo250 (Jun 29, 2020)

AudioGreg said:


> for bonus points, we have connected a phone handset into a wired RTS system, great pair up!



Any chance you can provide some details as to how you wired a handset into RTS? I'm hoping to wire Discord into our ClearCom system, but this solution is a little pricey: https://www.jkaudio.com/compack.htm


----------



## themuzicman (Jun 29, 2020)

Hopefully they’ll chime in with what they actually meant, but I read those comments to mean they simply wired an off the shelf handset with a 4-pin XLR to plug into an RTS pack, without dropping the $$$ for something like a Clearcom HS-6. The telephone hybrid you linked to is way overkill for the job.

To get bi-directional audio going into a clearcom system you have a few options, ultimately you need something with a nulling circuit in it to get send and receive on the same line -

1. Pick up a used IF4B or IF4W4, both are 4-wire interfaces, they take your normal Clearcom which is 2-wire (both send and receive on the same line) and separate them out into an input and an output. The big plus here is that you can independently set Discord into Clearcom and Clearcom into Discord. Secondary plus is that both options above can do up to 4 channels

2. More creative, use a spare belt pack and wire up a 4-pin XLR to whatever flavor of Discord source you’re using. Keep the belt pack latched on and there you go.


----------



## AudioGreg (Jun 29, 2020)

By phone handset I meant an android/iphone. The ComPack is what we used. Found one on eBay for $100. Provides an easy way to connect TRRS device to a 2W PL system. Also works with a regular telephone line. Having a remote user via telephone, or via app like Discord is a great feature in these days of physical separation.

The CC IF4B/IF4W4 rarely come up on the used market. The RTS SSA-324 offers 2 channels of conversion and much easier to find for well under $100. Both units do require a bit of DIY to connect, and tedious adjustments to perform optimally. Still a good solution if you get past that.


----------

