RailRoad Detector Question...

[Rayjk110]

Hello. On the railroad 'hot spot' detectors (the automated ones with the voice that is transmitted) what type of radio is used for this? And what is the power output of these? Just something that I've been trying to figure out for quite some time. I think I read one time that a Motorola Radius M10 is used, but I'm not sure. Thanks, Ray.

[sigmtr]

The proper term is a hotbox detector, or in more modern parlance a defect detector (hot journals, dragging equipment, overheight cars and broken wheels are some of the things that are detectable). In the not-so-distant past some roads used lunchbox style portables, but anything that will work off the 13.8V float-charged battery system can be used. I've seen various Radius and Maxtrac models personally. More than two channels is a waste, since it always stays on one.

Since the readout is intended for a train that has just passed the detector, the power is usually limited to 5 or 10 watts. This can be fed into a simple quater-wave whip on the roof of the bungalow, or you will see some locations with one of those heavy-duty "can type" quarter waves with the loop at the top. But they are never mounted very high; just above the roofline in most cases.

There are exceptions, of course. On the old GM&O line between St. Loius and Chicago they had some detectors tied into the dispatcher's remote base radios. Not sure if the UP ever changed that, but on a good day I could hear the Mazonia, IL detector on the other side of the state!

Doug

[Rayjk110]

Ok, thanks. Around where I live (CP Rail MP 42) the detectors can be heard about 15 miles away at best. How is the audio triggered for the hotbox detectors? I'm guessing it's more of a VOX setup somehow. Thanks, Ray.

[Rayjk110]

Thanks for the reply. Now, when the radio TX's, I'm guessing it's some sort of VOX configuration to a computer or something of the like?

[kf4sqb]

Probably depends on the manufacturer of the equipment used in the detector, for both questions.

We have older model Southern Technologies detectors we inherited from Norfolk Southern when we leased the rail line from them. The Southern Tech. uses, if I remember correctly, a Repco transmitter, putting out about 7 watts at VHF. As Sigmtr stated earlier, we use a 1/4 wave vertical on the roof of the bungalow the equipment is housed in for an antenna.

For your second question, I once again can only speak for Southern Tech. equipment, as that is all I have ever dealt with. On those units, the radio, power supply, interface board (connects the power supply, radio, all track-side equipment, and "logic board" together), logic board (contains the "brain" that the unit works from, as well as the "voice" it uses, which is stored on EPROMs), are all housed in one wall-mount chassis. The radio is directly connected to the interface board. The connections consist of B+, ground, audio, and PTT. The voice is actually stored as some sort of code in the EPROMs, and has a limited vocabulary (it can only say the words that have been programmed into it). The logic board circuitry "translates" the code into speech, and sends it directly to the radio, which it also controls the PTT line of. Any more questions? I'll answer them to the best of my abilities.

[kf4sqb]

Oh, and one more thing. The board is having some problems right now. It gives you an error message when you post a message, but it does get posted. It is just telling you, in a nutshell, that you will not receive e-mail notification when someone posts to the topic.

[Rayjk110]

Alrite, thanks for the info. I guess that makes sense on how everything is done there, but I haven't heard of Souther Tech before, that's a new one. Thanks for the info. Ray.

[Rwest25]

In the old days, the original "trade name of the industry" was Servo Corp.
Then along came Harmon Ind. Then GE jumped in and failed, Harmon took
over the GE HBD. Next Came Southern Tech. GE came back in and took over
Servo AND Harmon.
There are only two 2 players left.
Southern Tech specifies a Motorola CDM750.
I'm sure GE specs. a GE radio.

[kf4sqb]

In the old days, the original "trade name of the industry" was Servo Corp.
Then along came Harmon Ind. Then GE jumped in and failed, Harmon took
over the GE HBD. Next Came Southern Tech. GE came back in and took over
Servo AND Harmon.
There are only two 2 players left.
Southern Tech specifies a Motorola CDM750.
I'm sure GE specs. a GE radio.

Some years ago, in this area at least, the detectors were kind of divided down "road" lines. CSX almost exclusively used Servo Corp., and Norfolk Southern almost exclusively used Southern Tech. Now, CSX has gone to Southern Tech., and I don't know who Norfolk Southern is using.

Interesting to see that the newer Southern Tech. equipment uses an external mobile radio instead of the "integrated" Repco transmitter of the past. Would certainly make it easier to change frequencies, as the Repco units are rock-bound.

[Max-trac]

As for the antenna, I see a LOT of transit style on them out here in California.

Anyone have a link for FREQUENCIES of Hot Box detectors for Calif?

[kf4sqb]

If you know the main road frequency of the railroad in question, that should be what the detectors are on.

[k2hz]

I have noticed that CSX seems to be eliminating the PL tones on the detectors in my area. In Conrail days, the detector encoded 100.0 for "no defects" and 150.0 for an alarm condition. This worked with the detector function in the RR Spectra radios for TX lockout and a display indication when a detector was active and the 150.0 was also supposed to alert the Dispatcher when a defect was detected.

Since CSX took over, they have been making some changes in the detectors, apparently replacing the older units that were 25 or 30 W with 5 or 10 W units with no PL. Others that were first installed a few years ago that were originally lower power just encode 100.0 regardless of the detector reading.

I wonder if the use of the special PLs for detectors is being phased out in other areas?

[kf4sqb]

As far as I know, none of the detectors around this area have ever used PLs.

[Josh]

Here's what I know

Conrail's DED's were made by Parker in Sewell NJ circa 1985, the detector connected to a Uniden 2-channel radio (the kind that looked like a Moto model but can't recall the name). Channel 1 was encoded with pl of 100.0Hz and channel 2 with 150Hz, defects would trigger the radio to transmit on the 150Hz pl as indicated above. Conrail's old Aerotron-Repco clean-cab radios had a "TX Disable" LED and selectone boards installed that would disable the transmitter from working while a detector was going off- likewise the detectors were setup so that they wouldn't transmit over a conversation already taking place.

The HBD/DED/HWDs, of course were/are Servo branded- very robotic voice, of course there are about five different variations on those. These also used the Uniden 2 channel radios

The 'latest', at least for Conrail, detectors are made by GE/Harris and, speaking for the detector in-town, uses a Motorola GM300 radio with 100 and 150Hz encoding, using the channel steering pin settings. Aside from Wyandotte MI, these style detectors are known to exist elsewhere on the CR truncated system at CP-Croxton NJ, Morrisville PA, and Thorofare NJ, of course it seems that CSX controlling the former CR territories have replaced the original DEDs with this new-style DEDAC.

It's as easy as that.

-Josh

[Cowthief]

Hello.

The first time I came across this I was playing with military radio.
I was at a loss, as the military uses the same 100Hz and 150Hz tones.
150Hz will open the audio in almost all VHF FM military radios.
100Hz is the status OK tone.
So, this now sort of explains it.