Canon VCC4 Chain Connection Diagram

PC Com Port (M)--><--(F)-- Standard RS232 cable --(M)-->
<-(F)-- Black convertor--> (IN) 1st VCC4 (OUT) <--- Black convertor --(F)-->

<--(M)--NULL Modem Cable --(M)--><--(F)--Standard RS232 cable--(M)-->

<--(F)-- Black convertor --> (IN) 2nd VCC4

If cannot find NULL Modem cable (M-M),
You can use gender change (M-M) + Null modem cable (F-F) + Gender change (M-M)
= Null modem (M-M)