The way the NZBC network news worked before they were all linked up is absolutely fascinating:
The NZBC's microwave network between facilities was very much ad-hoc. Due to a shortage of microwave links, the network was completed by "off air" hops, where a 100 kW regional transmitter was received and re-transmitted by another. The network news was made possible by switching inputs to the regional transmitters, so that a signal could be relayed across the country. For instance, the Te Aroha regional transmitter for Hamilton could be switched away from Auckland programming to relay off-air, the Wellington signal coming up the country. Auckland then could see Wellington via Te Aroha. The non-synchronous switching was done manually initially and later with tone switching. During the network news presented from Wellington, if an inject was required from Auckland, Auckland would switch from transmitting Wellington pictures to transmitting, briefly a black screen with a small white "A" in the corner. Then each transmitter down the country would have to switch over so that the "A" would eventually appear in Wellington and beyond. Once all centres could see the "A" caption, the Auckland inject would be played. At the end of the item, the process would be reversed with a "W" for Wellington being switched sequentially, and then finally the Wellington presenter would appear again in all centres. The viewer would see a black non-synchronous switch which would take a second or so. Eagle-eyed viewers could see the identification letters change on the corner of the screen. Those with poor vertical hold would have to wait a little longer for the picture to stabilise. Occasionally, a transmitter would be switched out of sequence and the viewers would be treated to the sight of 100 kW of video feedback.
deejay, commseng and WW Update gave kudos