IT'S JUST AS WELL, we think, that Secretary of State Cyrus Vance ended his Geneva meetings with his Soviet counterpart with neither a SALT agreement nor a summit date in the bag. The one, scheduling of the summit, hinged on consummation of the other, a treaty limiting offensive strategic arms. These would have been regarded, at least tentatively, as major achievements. But one particalar issue that seems to have held SALT is central to the prospects of Senate ratification of a completed agreement, and it would have been quite reckless to accept an inadequate resolution of it just to wrap up the negotiations at this time.

This issue involves the relatively new Soviet practice of putting into a code defying American monitoring certain information or telemetry sent back by missiles being tested. The practice simply does not square with the Soviet-American pledge not to interfere with the other side's "national technical means" - electronic eyes and ears - of verifying compliance with a SALT agreement. This pledge was written into the SALT I agreement restriciting offensive missiles in 1972, and it is part of the SALT II pact being negotiated now. At Geneva, the American delegation asked for clear-cut restrictions on encoding telemetry. The Soviet response evidently was unsatisfactory. Differences were also reported on several other issues, including some that were previously resolved and tht were reopened by the Soviet side. Nonetheless, the gaps are said to be of the sort that can be narrowed by the respective SALT delegations in a relatively short time.

We hope so. But meanwhile it is worth underlining that telemetry is a lot more than one of those exotic, technical issues that make would-be readers of SALT stories turn to the funny pages. Telemetry goes directly to verification: the requirement, as much political as technical, that whatever is agreed on, the United States must by in a position to see that the Russians make good on their word. For a crucial swing bloc of senators on whom ratification of a treaty will rest, verification may be even more important than the marginal differences in numbers and terms that are all that could be expected to emerge from the final drafting of this treaty.

Indeed, given the way the nuts and bolts of SALT II have been machined by the technicians and bureacrats literally for years, the real SALT issue is whether the Senate thinks Jimmy Carter is a fit guardian of the nation's security in the overall context of Soviet-American relations. At this late hour, nothing could more surely undermine Mr. Carter's claim to be such a guardian than to have the impression cast that he was hasty or careless on an important aspect of verification. That is why, given the terms he was offered, there is no cause for undue dismay that Mr. Vance is returning from Geneva emptyhanded.