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Jonny 290 posted:are IMTS phones anachronistic enough for this thred? this is really interesting we threw away a bunch of radiotelephones designed for use with OLT (Offentlig Landmobil Telefoni) about two months ago when we cleaned the basement at the local ham radio club manual switching system, to receive calls you had to listen to a calling channel everywhere you went and then if someone called you an annoyed sounding lady would yell at you to switch to some other channel to take the call don't know if they allowed handovers at all, it would definitely require switching to the calling/operator channel to have them transfer it manually also if you wanted to call someone from a landline you'd better know roughly where they were, otherwise they'd have to try every transmitter in the county until they answered pretty sure they eventually added a selcal system, but i think that was around the time the glorious Nordisk MobilTelefoni system was introduced with ~digital~ in band signalling and automatic handover i'm not sure if all radios were duplex, but i have one which included duplex filters tuned to ~163 and 171 MHz
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Jan 14, 2016 22:14
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FrozenVent posted:the Canadian coast guard will still (or at least they did a few years ago) patch phone calls through to marine radios for like fishermen and stuff. it's a duplex thing so you can listen in to the shore side of the conversation if you're not a nice person... and transmit over the other ship if you really want to be a dickhole pretty sure most if not all marine radio services offer radiotelephone calls still, but i've never had the chance to try it despite having a marine VHF license i have an old marine VHF which included some kind of selcall/ANI thing, not sure how that system worked, there was no DTMF pad on it so I assume it either auto-transmitter the subscriber ID to the operator or it worked as a selcall. it also included a nice handset with PTT button, which is always nice to have in general they also did duplex telephony over MF/HF, or at least the navy used to. I have an Elektrisk Bureau  HF transmitter and somewhat matching ITT Mackay receiver, the service and installation manual includes descriptions of how to wire it into the ships telephone system and what kind of duplex filters should be usediirc they did downlink around 1800 kHz and transmit around 2200 or so. no idea if that could be automatically connected or if the ships radio operator had to set it up with the land station operator a later version of the exciter module included a remote control connector to set the frequency, which suggests some degree of automation
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Jan 15, 2016 17:28
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