Sentai Speculation: How I Believe Signalman Got Conceptualized!
Signalman in Carranger is an obvious parody of Robocop. Considering that Carranger itself is really more focused on cars than Turboranger and that they fought the Bowzock gangster, so I guess the producers thought that maybe creating a Robocop parody would fit the show pretty well.
In 1993, Janperson was created as a fully robotic version of Robocop. For some reason, I want to believe that Robocop even if he was an American-made character, ended up getting a huge soar of popularity in Japan. Jiban was also a Robocop-inspired hero except that he defeated monsters of the week while Janperson was more true to the Robocop theme... except Janperson was never a human revived into a cyborg.
So I was thinking,why did the producers behind Carranger decided that they needed a Robocop parody in Carranger? If you take a look at Carranger, the enemies were space gangsters. I would like to think of the Bowzock to be a parody of the gang members in Detroit. The Robocop TV series came out in 1994 so I wonder if that also inspired the creation of the Bowzock and even Signalman. While the Carrangers were fighting the Bowzock criminals from destroying Earth, the producers thought throwing a Robocop type joke might work for the show.
If Toei actually didn't copy anything from the Robocop franchise into their shows, it was the fact that Robocop was a man with a wife and a son. If you saw Jiban, the only family the main protagonist Naoto Tamura has on-screen is his sister. Janperson has no family except his own creator Kaoru Sagasa. However Signalman has one thing in common with Robocop - both law enforcers have a wife and a son! The twist was that Signalman's wife and son are also ROBOTIC? In the Robocop TV series, there was also some kind of strain between Robocop and his son... in Carranger, there was also some kind of strain between Signalman and his son Sigtaro. Maybe Signalman isn't really robotic but a mechanical lifeform capable of reproduction and maybe he's really wearing clothes made of metal for all we know.
As for Sirender, I am thinking that this robot might be a tribute to the Daileon Giant Robot in Juspion (another Metal Hero series). Juspion would use the Daileon Giant Robot to defeat the giant beasts. In Carra,ger, Signalman would launch the giant robot Sirender to defeat giant monsters. While he was at odds (at first) with the Carrangers but they eventually put their differences aside to defeat the bad guys.
What do you think?