I was a Pierce County Wa. State Paramedic in the middle 1970's, and remember the "MEDCOM" radios well. Actually sent an EKG very well to the ER Doc! (Not too much artifact) Happy Holidays and 73's Tim Hardy W7TRH/AFA5TP Vashon Is. Wa.
-------------- Original message -------------- From: Doug Dickinson <dougd...@yahoo.com> There were two basic repeat modes used in the Medical Telemetry systems. The Med 1 through 8 and the two dispatch channels (now known as Med 9 and 10) are duplex channels. The Orange Box and the Apcor (both Motorola) and some others were duplex hand carried units. I will focus first on the Orange Box and The Apcor. Both units were duplex and transmitted to the base on the traditional mobile higher frequency. The orange Box had a repeat function that would retransmit the base TX freq through the mobile freq. The base station ran in duplex mode, not repeated. This way, a portable radio (like a COR HT220 model) would transmoit through the Orange Box to the base and the base would transmit through the Orange Box to the portable. The portable was also configured like a base station channel-wise. It worked! The 12W APCOR worked the same way. The EMD mobile repeater was a duplex Micor 10 channel radio with a separate Pac_rt radio receiver. The mobile would transmit on the mobile freq and would receive on both the Base channel and a 458MHz channel (there are 4 of them) simultaniously and repeate the audio back out through the mobile freq. The base would operate in non-repeated mode. The would allow a full-duplex conversation, although it isn't technically full duplex - it just works that way. The porable unit talking to the Mobile was a 1 watt APCOR radio that talked on the 458 channel and listened on the 468 channel, thereby giving the entire conversation duplex functionality. So - that's how all this worked. The Mobile and APCOR portable combined cost almost $5K in the mid-late 70s. That was more than a car cost! Motorola has lots of bells and whistles on it. The mobile was SP all the way and the APCOR was a costly device. Doug in Seattle now, Florida then
