John: I own a 4952+18179, which is very similar. The manual might be available $25 for one week. Answers as follows: (a) I believe you can save the data to the tape drive. My version has the "02 option" which is a memory board which contains about 700k of RAM and 128k of battery-backed NVRAM. Your unit may or may not have that option. (b) My unit has a floppy drive, but I recall reading that the tape drive uses standard QIC tapes (don't recall the type, DC60 or DC100 I think). They should be available from various sources including eBay. (c) The vertical row of switches on the 18179 enables you to pass through or isolate various RS232 signals from the analyzer. The horizontal row of 25 switches and patch cable holes enable you to concoct various wiring schemes. (d) I believe that you can connect the video to any standard composite monitor and it will show whatever is on the internal screen. Rich -----Original Message----- From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org] On Behalf Of John R. Hogerhuis Sent: Friday, February 17, 2006 11:52 AM To: General Discussion: On-Topic and Off-Topic Posts Subject: Help with HP 4951B protocol analyzer + 18179A Anybody know much about this device or have a manual? I bought it for $10 off ebay to test serial comm protocols on some of my vintage projects. It works with some caveats: a) If it's off (but plugged in) it loses its memory. Is there a backup battery inside that can be replaced? b) The tape drive may or may not work. Not sure I'll ever really need it. What kind of tapes does it use, and can they be acquired c) I'd be interested to know what the switches on the 18179A do. d) What can I hook the external video interface to? Thanks, -- John.