Federal’s ‘Director’ and ‘Interceptor’ Electronic Sirens

By: Leslie Erlich

So you found a 1970 Superior/Cadillac 54′ high headroom ambulance that is rusting away and you want to restore it to the way it was when it was new.   The beacon and siren are long gone but you have a idea of what type of warning equipment it had when it was first put into service.   Beacons are fairly easy to find – either a Federal 17 series or 184 series will do.  But what about the siren?  Should you go mechanical or electronic?  According to the 1970 Superior catalogue, there were three mechanical siren options: A Federal Q, a Federal C6, or a B&M Super Chief.   As far as electronic sirens go, only the siren speakers are illustrated in the catalogue: a Federal CP25, CJ24, SA24, and CJ184 speaker/light. But if the speakers were Federal, chances are the siren would have been a Federal Director or Interceptor.

If you choose to go with an electronic siren, the Director and Interceptor models are by far the most recognizable among the old Federal electronics, particularly the ‘brown face’ Director and the ‘blue face’ Interceptor.  The brown face and blue face versions were in production for about twenty years, and on the surface they look pretty much the same regardless of when they were made.   To the uneducated observer, a siren is a siren is a siren.  But I will argue that surface appearance alone is not a valid indicator of period correctness.  The Director and Interceptor sirens underwent several design changes throughout the course of production, and in my research I have found that the sound of the siren is the best indicator of period correctness.

PA5 and PA10

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The very first Director and Interceptor sirens were the PA5 and PA10, and they only vaguely resembled their brown and blue faced cousins.  The Director was intended to be the ‘economy’ model while the Interceptor would be the ‘deluxe’ model.   The most significant features about both sirens are that the Director has a wired-in microphone and screw terminals for power/speaker/radio connection, while the Interceptor has an optional detachable microphone and multi-pin plug connectors for the radio, speakers, and power supply.   The PA5 (Director) and PA10 (Interceptor) had black control panels and grey plastic knobs, and they were both capable of producing the standard wail and yelp tones that are still featured on electronic sirens today.  But the one thing that really set the PA5 and PA10 apart from later Federal electronic sirens is that these models were designed to simulate the sound of a mechanical siren.  I’ve heard a PA5, and the ‘wail’ tone sounds much like a Q2b mechanical siren.   The PA5 and PA10 were in production from about 1960 to 1962, and either one in working condition would be a rare find.

PA5 sound sample: pa5

PA15 and PA20

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The brown face / blue face era began with the PA15 and PA20 around 1962.  What sets these sirens apart from later versions of the Director and Interceptor is that both models have wail, yelp, and ‘alert’ tones.  The ‘alert’ tone is just a steady tone that plays at constant pitch – it doesn’t rise or fall.   Federal abandoned the simulated mechanical tone in favor of a more rounded synthesizer-like tone when the PA15 and PA20 were introduced. The sound of these sirens is much deeper and lower-pitched than what we are accustomed to hearing nowadays.  I’ve never heard a PA15 or PA20 in use on a ‘real life’ emergency vehicle, but I have heard the PA15/PA20 sounds on many TV shows and movies that were produced from the late 1960s right on up to the early 1980s.   For example, the siren sounds that were dubbed in for Squad 51 of Emergency and the patrol car on Adam-12 were a recording of a PA15 or PA20 running in ‘manual’ mode.  Or the dual siren tones of the police cars on Hawaii Five-O were overdubs of  PA15 / PA20 wails and yelps.  Over the course of production the PA15 and PA20 underwent several minor internal design changes, but the circuit board layout remained roughly the same until the end of production.  Letters at the end of the serial numbers indicated revisions to the circuitry, such a F1, E1, F1A, E1A, F1B, E1B, etc.  PA15 serial numbers began with ‘F’ and PA20 serial numbers began with ‘E’. Production of the PA15 and PA20 ended in 1966.

PA15 / PA20 sound sample: pa15pa20

Early PA15A and PA20A

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The PA15 and PA20 were replaced by the PA15A and PA20A in 1967.  The PA15A has wail and yelp tones only while the PA20A has wail, yelp, and hi-lo tones.  The hi-lo tone is an electronic simulation of the hi-lo horn sirens that were used on European ambulances.  With the change in the control panel layout came a complete change in the design of the siren oscillator circuits. The early PA15A and PA20A models also had deep low-pitched tones, but the wail and yelp tones rose and fell a little differently than those of the PA15 and PA20.   The wail tone rose more slowly, and the yelp had a distinctive throaty ‘wah-yu wah-yu wah-yu’ sound, almost like a human voice.   PA15A serial numbers began with the number ’1′, while the PA20A serial numbers began with the number ’2′. The first number was followed by a letter – A, B, C, or D, and the letter indicated that there were changes to the circuitry.  I’ve never seen an A series unit, so I’m assuming that it was either a prototype or demonstrator that never made it to full scale production.  There are service manuals for the B, C, and D series however.  The early PA15A and PA20A sirens were in production from 1967 to about 1970, although there seems to be a lot more 1D and 2D series units around than the earlier versions.

Early PA15 / PA20A sound sample: early15a20a

PA15A series 1E and PA20A series 2E

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The Director and Interceptor siren oscillator circuits would undergo one last major change in the early 1970s. These units have the letter ‘E’ in their serial numbers. The circuit boards in the E series units are completely different from the earlier PA15A and PA20A units. The new models, PA15A series 1E and PA20A series 2E, would have high-pitched wail and yelp tones much like the electronic sirens we hear nowadays. Sometimes I have to listen closely to tell the difference between a Federal PA15A 1E or PA20A 2E and a Carson/SVP SA450! One possible reason for going to the higher pitched sounds was that more compact speakers were coming into use, and smaller speakers reproduce higher frequency sounds better than low frequency sounds.  Federal’s TS100 speaker, the same speaker that is used in the TwinSonic light bar, is one such example.    I first heard the high-pitched E series PA15A/PA20A sounds around 1973, although someone told me that the circuit was introduced in 1970.   In any case, the PA15A series 1E and PA20A series 2E were in production throughout most of the 1970s and ended in the early 1980s. The 1E and 2E use 2N2925 transistors in the siren oscillator circuit, and the 2N2925 circuit was also used in the PA150, PA200, and PA1000 sirens. Besides the high-pitched wails and yelps, the other thing that makes the 2N2925 circuit unique is that goofy ‘in-between tones’ can be heard simply by turning the selector knob between wail and yelp or yelp and hi-lo.  The E series are by far the most common version of the Director and Interceptor, but remember that they are 1970s models and were in production when many ambulance companies were switching to van-based units.

PA15A 1E / PA20A 2E sound sample: highpitch

Chassis covers

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In terms of outward appearance, the chassis cover is the most distinguishable feature when comparing the PA15 / PA20, early PA15A / PA20A, and PA15A 1E / PA20A 2E.  The PA15 and PA20 have a short chassis cover, the early PA15A and PA20A have a long chassis cover with small ‘grille’ at the back, and the PA15A 1E and PA20A 2E typically have rows of holes on the back half of the chassis cover for ventilation.  The latter two chassis covers are interchangeable, so a cover is not a reliable indicator of period correctness.  I have a PA20A 2D with a 2E chassis cover, and on the surface it does look like a 1970s PA20A.

Circuits

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The circuit board is the most important part of the siren.  This is where the wails and yelps com from, and the sounds of the sirens changed along with the circuitry.  I have the three basic variations of the blue face Interceptor siren: a PA20, an early PA20A, and a PA20A series 2E.  The circuit boards of all three sirens are entirely different, and they sound different too! The PA20 circuit board is brown, the early PA20A circuit board is a cream colour with a set of wires running over top, and the PA20A 2E board has all wires running underneath.

Identification labels

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The serial number is stamped into a metal plate on the bottom of the PA15 and PA20, while the PA15A and PA20A have a silver-grey label on the bottom.  There are at least nine different versions of the PA15 and PA20 and five different versions of the PA15A and PA20A.   So for example if you have a PA20A with the serial number E1C, then you need to get a PA20 series E1C owner’s manual with the component location and schematic diagrams.  Or if you have a PA15A series 1B, you need a PA15A 1B manual.  A 1E manual won’t help because the board layout and components of a 1E are entirely different compared to the 1B.

So, returning to that 1970 Superior 54” high-top ambulance restoration – which siren to install?  Either a PA15A series 1D or a PA20A series 2D.   A 1B or 1C or a 2B or 2C would also be period correct.  All of these variations have the deep low-pitched slow rising wail and yelp tones.   Even a PA15 or PA20 would work, although they are much older sirens.   And if you can’t find any of the above, a mechanical siren will do.

Leslie Ehrlich

Leslie Ehrlich is a self proclaimed  ‘armchair pro-car ambulance enthusiast and a siren fanatic’.  We would like to thank him for sharing his extensive knowledge of the history of electronic sirens and warning equipment.

Electronic Sirens on Emergency Vehicles
ANOTHER “FAILED EXPERIMENT” FROM THE SIXTIES?
By
Kevin O’Connell

Are you still wearing corduroy bell bottoms? Nehru jackets? Beatle boots? Shag haircuts? Paisley shirts? Ben Franklin sunglasses?

Do you still refer to a raincoat and wading boots as turnouts? Do people still ride your tailboards with impunity?

Listening to “Boss Hits” on your 4 track? Driving a “really groovy” VW bus with tie-dyed curtains?

Hopefully your answers to these questions are all emphatically negative. Thankfully many of you are too young to remember the embarrassing things people did twenty five to thirty years ago (as if you could care – you’re too busy tattooing and piercing yourselves so you’ll have something to be embarrassed about in the future).

Why then, do many agencies still cling to another bad idea from the sixties; the electronic siren? After all, they seem to do a better job of instilling false confidence than actually warning other drivers. The answers and excuses I’ve heard over the years are numerous and nearly always rooted in myth or ignorance. In the interest of brevity, let’s just debunk the three most common notions:

Myth #1 – Electro-Mechanical sirens are too loud.

Probably the most illogical and emotionally-charged claim offered by opponents of real sirens. People who make this claim usually have to depend very heavily on their air horns to break intersections. They base their stance on the notion that real sirens are the primary cause of hearing loss among firefighters.

FACT: The biggest threat to your hearing comes from simply riding on your apparatus. For nearly fifty years the fire service has embraced cab-forward designed apparatus in which the entire crew becomes intimate with a large, high-powered noise generator; the engine. This is especially true of the poor slobs who ride in the jump seats. Why? Because this is a continuous noise. Unless you’re staged at a large campaign fire, chances are you’ll be exposed to this hazard most of the time in the apparatus.

Here’s how it works: Large engines with their heavy rotating and reciprocating masses set-up a low frequency harmonic effect of substantial amplitude. This type of noise doesn’t need your ears. It is conducted through the bone around your ears. Instead of the eardrum gently working the malleus (hammer) in your middle ear, all of the middle ear is overwhelmed. It’s not hard to imagine the devastating effect that long-term exposure could have. As a staunch advocate of communications headsets, it pains me to admit that headsets and hearing protectors do precious little to protect against low frequency harmonic effect, and in some cases, can actually exacerbate it. Some protection can be provided by a thorough application of sound barrier insulation. On the bright side, the fire service has finally accepted tilt-cab designed apparatus, which significantly reduces engine noise by eliminating the need for an engine cover with large openings. Considering the many significant advantages of tilt-cab apparatus, it’s disgraceful that it took something like axle weight laws to strike a blow for progress.

By the way; headsets and hearing protectors provide excellent protection against the sound generated by sirens. Some people are so anal about siren noise that they take things to ludicrous extremes.

I once had a fairly well-respected battalion chief tell me that he had succeeded in eliminating real sirens from his department’s front-line units. He went on to brag about how he had reduced electronic siren noise in his cabs by building insulated plywood boxes around the speakers. I was astonished. This guy didn’t have a clue! His department had locked into one brand of apparatus and let the salesman spec the warning devices.

The manufacturer had mounted light bar speakers with a horn opening of 5″ x 8″ behind the bumpers with openings of 3″ x 4″. It doesn’t take a genius to realize that this arrangement forced a great deal of speaker output to be deflected back under the cab, making almost as much noise in the cab as in front of the vehicle.

More importantly, actual sound output to the front of the vehicle was compromised to the point of being nearly ineffective. When I diplomatically explained these things to the chief, his response was tantamount to “Don’t confuse me with logic, reason and facts. My mind is made-up!”

Electro-mechanical sirens don’t continuously operate at full volume. Electronic sirens do. Comparisons of time-weighted average (or TWA, a favorite OSHA term) noise levels during emergency responses usually come-out fairly even, with real sirens faring better, especially on long runs.

Myth #2 – Electro-Mechanical sirens use too much current.

Like the arguments used against electric driveline retarders, this claim is based on the gristle-brained notion that simply bolting a real siren on your rig will automatically add a continuous 100 amp load to your electrical system, killing the batteries and wreaking havoc with sensitive electronics and communications equipment.

FACT: Real sirens only draw current during wind-up and full wail. Electronic sirens draw current continuously while activated, albeit at a lower rate. That lower rate is misleading; It has been estimated that six to eight electronic sirens would be needed to do the work of one real siren.

The real battery killer is the operator who leaves his vehicle idling for extended periods of time while lit-up like the Las Vegas Strip. Every 50 watt halogen lamp you put on your vehicle adds about 4.2 amps of load while lighted. The continuous siren load myth is often invoked by people trying to justify the use of large alternators and/or battery arrangements. While I advocate using six-pack battery arrangements and large alternators, I cannot condone misleading people about imaginary electrical burdens.

A few years ago, while touring the repair facility of a large fire department on the southern coast of California, I noticed a lot of holes on apparatus where real sirens had obviously once been mounted. When queried, the shop foreman (a good friend) told me that his department had decided to remove their real sirens to reduce battery failures. I asked, Truthfully now, have you noticed any difference?” He sheepishly grinned and said “No, not really”. Within a year real sirens began to mysteriously reappear on the rigs.

When it comes to load-induced battery failures, it is important to remember this: 1) Alternators are intended to sustain loads. They are not battery chargers. 2) No matter how large, alternators do not produce full current capacity at idle.

Incidentally, load managers are becoming increasingly popular on fire apparatus. These devices are a great innovation. They sequentially switch lighting loads on and off minimizing voltage spikes. When battery voltage begins to drop, loads are sequentially shed until voltage stabilizes. Additionally, some private ambulance operators are enjoying success with isolated siren battery circuits.

The most popular real siren draws 105-125 amps at full wail, a momentary load imposed only a fraction of the time during a response. A Los Angeles manufacturer guarantees their real sirens will draw 70 amps or less at full wail, which is less than the continuous load of many emergency warning light systems.

A very heavy 25% cycle during a response would average 17 1/2 amps continuous load. (Kind of makes your 55 amp air conditioner seem pretty decadent, doesn’t it?)

Moderate in-rush current of a flashbulb’s duration seems to be an electrical evil spirit to intellectually-challenged critics, who consistently fail to realize that there is an equally brief voltage spike (more dangerous than voltage drop) upon de-energizing. These are traits common to electrical loads. If a real siren is a villain, then your vehicle’s starter is a mass murderer!

Myth #3 – They cost too much!

A real siren will typically add $1,500 to $2,000 to the cost of a new fire apparatus. This is offset several times over the life of the rig by never having to listen to an airhead, finger in nose, saying “I never heard the siren! I’m suing!” (My personal favorite – “Why do you have flashing white lights on your roof? What do they mean?” The correct answer – “They don’t mean anything. The salesman told me to buy them”.)

Actually, it doesn’t take an airhead. Nearly everyone has a personal horror story about a near disaster involving an anemic peanut whistle. My wife came close to being creamed on several occasions in the city where she works. Another agency that bought what the salesman told them to. Their “Chevy Corvair” pumpers (rear engine, insufficient front axle weight) were equipped with siren speakers which weren’t even approved for use in our state! If those twits had hurt my wife, I’d own that city today.

Let’s face it – most traffic collisions involving emergency responses bring-out litigious land sharks. And they usually have a case.

My own chief chastised me a few years ago for outfitting a new rescue squad with a real siren. I backed it up with a dual amplified electronic, each amp driving a 200 watt speaker.

The siren and two speakers were mounted out front on a push bumper for maximum effect. “That thing has too much siren!” the chief complained. “Take all of that crap off. It looks too aggressive. We didn’t do it that way in (his former agency)”.

It was all I could do to keep a straight face. At that moment his former employer had two engines out of service for “I never heard the siren” collision repairs! That chief is long gone, “all that crap” is still there, and the vehicle in question has never been involved in a response-related accident.

The seemingly high initial cost of a real siren is misleading. Unless you specify a siren, most manufacturers will use a cheap throw-away box. As many people have reminded me, the life expectancy of an electronic siren is a fraction of that of a real siren.

Besides the cost of numerous replacement boxes and speakers over the life of the vehicle, the hidden cost of downtime and equipment changeovers to a reserve rig is substantial. That little peanut whistle wasn’t such a bargain after all, was it?

If all these arguments haven’t penetrated that cartilage between your cars, please consider this: Electronic sirens are directional, especially when used with unconventional speakers. Real sirens are omni-directional.

Electromechanical sirens work as well to the sides of the vehicle as they do to the front. While it can certainly be argued that vehicles ahead of you present a risk, they are more of an annoyance compared with an even greater hazard: Those vehicles you can’t see – and those vehicles that can’t see (or hear) you!

(Kevin O’Connell is an emergency equipment specialist and President and CEO of B&M Siren Company. His articles have appeared in many prestigious national fire engineering publications, and we think him for offering this article for publication..)