CMED Radio Programming
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They aren't simplex, they are duplex, or at least were designed that way so that phone like full duplex conversations could be held between field personnel and hospital personnel.
The base (hospital) side is on the 468Mhz frequencies, the ambulance side is on the 463Mhz frequencies. Med 4 is repeated, at least in MA where it is the calling channel. In other parts of the country Med 10 is the calling channel.
Some of the Metro-Boston channels are repeated, but for the most part they are not.
The base (hospital) side is on the 468Mhz frequencies, the ambulance side is on the 463Mhz frequencies. Med 4 is repeated, at least in MA where it is the calling channel. In other parts of the country Med 10 is the calling channel.
Some of the Metro-Boston channels are repeated, but for the most part they are not.
N1BHH
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Gary, you have that reversed somewhat. The mobiles transmit on the 468 range while the hospital transmits in the 463 range.
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Oops, you're right. Should've paid more attention to that!
creeperjeep
Lit GMRS
Is it necessary to have CMED transmit ability if you aren't clear on how its used?
I believe the OP was asking for advice on how to program it into his portable scanner; he will not have any "transmit ability".
It all depends on location as well. The CMED Disp Center, and the Hospitals will transmit on the lower freq through the transmitter. While the higher freq (468) will be simplex, and unless you are fairly close to them you will typically not hear the entry not side of the convo. The frequencies are used to (Depending on the region) coordinate EMS in an MCI, Coordinate Med Flight, give entry notes to a hospital, contact on-line medical control, and for a few more tasks. In some parts of Mass, Med-9 and Med-10 are reserved for Hospital/City based EMS services. For example In Region 3 (Lawrence) Med-9 is used for Greater Lowell and Greater Lawrence ALS service. They are dispatched by CMed Lawrence and use the duplex system. In Region 2, UMass Memorial EMS (AKA Worcester EMS or WEMS) used Med-9 and it was repeated. Now that channel is used to coordinate Mutual Aid EMS into Worcester. And Boston, Boston EMS uses Med-9 and Med-10 for operations, and both are repeated. If you are near Boston, you can typically hear Med Flight entry notes going into the city if you are in a good spot because they transmit from up high.
Very few radios are full duplex anymore as they are quite expensive. I would hazard a guess that CMED removed that requirement from the radio specs a long time ago.
In CT (and I suspect MA as well), many of the hospitals do not use radios, instead they have dedicated phone lines from the CMED center to each hospital. The call to the hospital is really a really a radio call to CMEDs tower and then a radio-phone patch to the ED. During major incidents they do bed counts and those are not heard over the air. The CMED operator can also shut off the repeater portion of the call so you would have to monitor both sides to hear a complete patch. The mobiles are obviously weaker than the CMED portion so you have to be up high or nearby. Even more so if the EMS worker is using a portable. If you are programming a scanner, I would suggest putting the mobile freq first (468.xxxx) and then the base (463.xxxx). If they are not using a repeater, you may get an open carrier through the base side. It would lock up the scanner and you would not hear the patch.
chris
In CT (and I suspect MA as well), many of the hospitals do not use radios, instead they have dedicated phone lines from the CMED center to each hospital. The call to the hospital is really a really a radio call to CMEDs tower and then a radio-phone patch to the ED. During major incidents they do bed counts and those are not heard over the air. The CMED operator can also shut off the repeater portion of the call so you would have to monitor both sides to hear a complete patch. The mobiles are obviously weaker than the CMED portion so you have to be up high or nearby. Even more so if the EMS worker is using a portable. If you are programming a scanner, I would suggest putting the mobile freq first (468.xxxx) and then the base (463.xxxx). If they are not using a repeater, you may get an open carrier through the base side. It would lock up the scanner and you would not hear the patch.
chris
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Not very few, I'd say none. During the 1970s Motorola and GE made full duplex radios for CMED use. In Motorola's case, they used UHF Micors with duplexers built in and the audio modified for full duplex. They also made a radio called the APCOR, which was essentially two MX300 radios with a duplexer, a high powered PA, and other features. Heavy as all hell, but I digress. GE made version of their Mastr II (I think) in UHF. The Motorola radios had dual control heads, one for the front and one for the rear of the ambulance. There was even a transmit inhibit feature so the two control heads could communicate with each other as an intercom.
They were expensive and a nightmare to maintain.
When Motorola introduced the Syntor, the Micor based MEMCOM went away. The APCOR was discontinued around 1990. Since then I'm not aware of any full duplex med radios being offered by anyone.
Pretty accurate. The Metro Boston CMED uses a computer controlled switching network to patch hospitals to base stations, select channels for multi channel bases (most are four channel bases) and the system allows more than one hospital to be patched on the same base at the same time. I don't know what other CMEDs do, but I think Bristol County uses permanently assigned channels which are dialed up by CMED when a patch is needed.
Springfield uses both UHF 463.xxxx and 155.3400 with DTMF access directly to the hospital. The CT service I used to work with did not have VHF so when we went to MA, we used Med 4 for calling and then were patched to the hospital via one of the other med channels.
chris
chris
E911dispatch
Newbie
Worcester CMED - Region II
In Region II Med-4 is not repeated. The repeaters on each tower can be opened if need to make other units aware of traffic calling in when multiple units are on the air. The original reply is also correct, you will not be able to hear the ambulance side of the patch unless the repeater on the tower the operator is using is open. Med-1 is reserved for Mary Lane hospital, Med-3 for Athol Memorial (direct hail channel) Toned by the operator after signing on, Med-6 for Heywood also direct hail. Med-9 is used primarily for WEMS mutual aid (normally a private service) and an open Med channel is used for ALS intercept and inter-agency communications initiated by the operator. You have to be very close to the truck to hear their side of the entry note. MCI traffic is given a dedicated channel and a repeater is opened, this channel is at the discretion of the operator and is normally a higher channel.
In Region II Med-4 is not repeated. The repeaters on each tower can be opened if need to make other units aware of traffic calling in when multiple units are on the air. The original reply is also correct, you will not be able to hear the ambulance side of the patch unless the repeater on the tower the operator is using is open. Med-1 is reserved for Mary Lane hospital, Med-3 for Athol Memorial (direct hail channel) Toned by the operator after signing on, Med-6 for Heywood also direct hail. Med-9 is used primarily for WEMS mutual aid (normally a private service) and an open Med channel is used for ALS intercept and inter-agency communications initiated by the operator. You have to be very close to the truck to hear their side of the entry note. MCI traffic is given a dedicated channel and a repeater is opened, this channel is at the discretion of the operator and is normally a higher channel.
" Duplex " might mean 3 things in this thread -
1. receive and transmit on different freqs (maybe "half duplex" to some people) (maybe also called "three way" by some people) (like taxi cabs)
2. repeater or non repeaterized ops
3. listen and talk at the same time ("full duplex" or "duplex duplex" as I like to call it)
Boston EMS seems to have the ability to use 462.95 in duplex, simplex, and half duplex modes. I am not sure if the BEMS dispatchers can receive and transmit at the same time on 462.95. I also dont know if the BEMS dispatchers can hear any field units that might be using 462.95 in direct/simplex mode.
Maybe the simplest way to sort this all out is to determine
- what freqs are the field units transmitting and receiving on ?
- what freqs are the dispatchers transmitting and receiving on ?
- are comms being "repeated" ?
- can anyone receive and transmit when someone else is receiving or transmitting ?
- can anyone receive and transmit at the same time ?
Peabody FD is the only nearby agency that I can think of where the dispatcher can hear the field units if they are on "direct" (they call it Channel 2)
1. receive and transmit on different freqs (maybe "half duplex" to some people) (maybe also called "three way" by some people) (like taxi cabs)
2. repeater or non repeaterized ops
3. listen and talk at the same time ("full duplex" or "duplex duplex" as I like to call it)
Boston EMS seems to have the ability to use 462.95 in duplex, simplex, and half duplex modes. I am not sure if the BEMS dispatchers can receive and transmit at the same time on 462.95. I also dont know if the BEMS dispatchers can hear any field units that might be using 462.95 in direct/simplex mode.
Maybe the simplest way to sort this all out is to determine
- what freqs are the field units transmitting and receiving on ?
- what freqs are the dispatchers transmitting and receiving on ?
- are comms being "repeated" ?
- can anyone receive and transmit when someone else is receiving or transmitting ?
- can anyone receive and transmit at the same time ?
Peabody FD is the only nearby agency that I can think of where the dispatcher can hear the field units if they are on "direct" (they call it Channel 2)
RKG
Member
Putting aside terminology:
1) A transceiver can receive or transmit, but not both at the same time.
2) A typical station (e.g., Quantar) has independent transmit and receive capability, and it can receive and transmit at the same time (so long as the Rx and Tx are on different frrequencies).
3) In a typical dispatch design, the dispatcher's speaker is wireline connected to the station's receiver and his mike is wireline connected to the station's transmitter (in both cases, through the comparator). The dispatcher can transmit and listen to subscribers at the same time. In addition, if the system is repeated (i.e., one transmitting subscriber can be heard by other subscribers), and if the comparator is so programmed, a subscriber can barge in over dispatch transmissions and be heard (at slightly reduced audo levels).
I believe that the accepted terminology is:
Simplex: all stations transmit and receive on the same frequency.
Duplex: dispatch transmits on F1 and listens on F2, while subscribers listen on F1 and transmit on F2. If such a system is not repeated, it is sometimes referred to as "two-frequency simplex." Some such systems are sometimes programmed to emit beeps on F1 while one subscriber is transmitting, to indicate that the F2 is in use and other subscribers should wait to transmit.
Repeater: a duplex station programmed such that activation of the station's receiver (non-voted) or the vote bus line (voted) activates the station's transmitter and passes received or voted audio to it, without any action on the part of the dispatcher required.
Half-duplex: a transceiver.
Full duplex: a station capable of receiving and transmitting at the same time.
Also keep in mind the current med channels are being split into twenty,to comply with the narrow band requirements.I know region 3 will then operate on one p.l. number instead of the current 2 for the north shore and merrimack valley,All of region 3 tower sites(all 13 of them) will be updated easily.The ambulance services that use the cmeds will have to have radio equipment to comply with the new channel plan.
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The CMED system was originally intended to be not only full duplex, but multiplex. In the original 1970s configuration paramedics were supposed to be able to send EKG data and talk to medical control simultaneously. In addition, medical control was able to talk to the paramedics telephone style.
Both the Motorola "MEMCOM" radios and the Apcor radios of the time were capable of full duplex operation. In addition, the Apcors could serve as repeaters and had Vox capability.
When Motorola announced that they were ceasing production on the Apcor in about 1990, the Boston system was built out to allow bedside communications using 4 watt portables. The flavor of the early 1990 was Motorola Sabres. About the same time, the MEMCOM became obsolete along with the Micor radio it was based on.
A couple of years later full duplex capability was gone from most places, although I saw a few MEMCOMs in service in places like New Bedford (I think) until the late 1990s.
That is different than what was seen on Emergency, but back then in LA County they were using a VHF system if I remember correctly.
In the original configuration only Med 4 was intended to be repeated, but in Boston Med 8 was repeated as well due to the medical control configuration. During the 1980s, the medical control doctor was not required to be in the hospital and in fact could be anywhere in Boston. He had a MT-500 set on Med 8 and the repeater was turned on. That went away in the mid 1980s when attending physicians started to staff Boston City Hospital's ER 24/7.
Why Med channels are still repeated in some cases is something I don't know, but can find out.
RKG, in regards to your point 3). Some systems (BPD, BEMS) are SP so that if a subscriber talks over the dispatcher the subscriber signal is repeated, but that the norm is that the dispatcher only can hear the subscriber if the dispatcher is transmitting and a subscriber breaks in. I know that when we first went to the Centracom II, the dispatchers could hear, but the signal was not repeated.
I know of some wise guys who would whisper sweet nothings into the female dispatchers ears. Imagine their surprise when the system was changed and their comments went out for the world to hear.
Both the Motorola "MEMCOM" radios and the Apcor radios of the time were capable of full duplex operation. In addition, the Apcors could serve as repeaters and had Vox capability.
When Motorola announced that they were ceasing production on the Apcor in about 1990, the Boston system was built out to allow bedside communications using 4 watt portables. The flavor of the early 1990 was Motorola Sabres. About the same time, the MEMCOM became obsolete along with the Micor radio it was based on.
A couple of years later full duplex capability was gone from most places, although I saw a few MEMCOMs in service in places like New Bedford (I think) until the late 1990s.
That is different than what was seen on Emergency, but back then in LA County they were using a VHF system if I remember correctly.
In the original configuration only Med 4 was intended to be repeated, but in Boston Med 8 was repeated as well due to the medical control configuration. During the 1980s, the medical control doctor was not required to be in the hospital and in fact could be anywhere in Boston. He had a MT-500 set on Med 8 and the repeater was turned on. That went away in the mid 1980s when attending physicians started to staff Boston City Hospital's ER 24/7.
Why Med channels are still repeated in some cases is something I don't know, but can find out.
RKG, in regards to your point 3). Some systems (BPD, BEMS) are SP so that if a subscriber talks over the dispatcher the subscriber signal is repeated, but that the norm is that the dispatcher only can hear the subscriber if the dispatcher is transmitting and a subscriber breaks in. I know that when we first went to the Centracom II, the dispatchers could hear, but the signal was not repeated.
I know of some wise guys who would whisper sweet nothings into the female dispatchers ears. Imagine their surprise when the system was changed and their comments went out for the world to hear.
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