Tektronix 147A

Gen-lock capable of locking to most helical scan VTR's
Can operate as a master-sync generator or fully or partially timed from external sources
Front-panel pushbutton selection of external synchronization is provided
In external mode:
locks on composite video (1 V)
composite sync (-4 V)
reference subcarrier (2 V)
Two front-panel lights show subcarrier and/or sync external lock
Other features include:
simplicity in operation
compact and economical
simplified timing via multiple subcarrier phasing controls
All inputs and outputs are located on rear-panel