Safeguard is unpaid content that plays during ad breaks when there is nothing else available. In other words, when there are no ads, PSAs, or filler available for the listener, it goes to safeguard. It is the last resort before "dead air."
Note: safeguard is not the same as filler! Filler (station promos, PSAs, sweepers, etc.) is intended to be played on a schedule or when you are low on paid ads; safeguard only plays when there is a problem somewhere.
This article explains why you might hear safeguard playing when you don't expect to.
Short Explanation
The most likely explanation is a problem with inventory management caused by frequency caps that are set too high -- including frequency caps on your filler content -- along with targeting criteria that is too specific. The result is lower avails than you want, so your ads and filler sit there unplayed because they are capped against playing to many of your listeners. (Remember that Tap ads play one-to-one, i.e., ads are served individually, to each listener.)
The solution is to review your campaign targeting and frequency capping, and to loosen them up. See the tips at the bottom of this article.
Detailed Explanation
Safeguard sometimes plays even when you have plenty of campaigns that seem to match up with your inventory, and sufficient filler. To understand why this happens you must consider that Tap ads are served individually to each listener, in a one-to-one relationship. This is achieved through Tap's targeting and serving technologies, which view each listener as a unique opportunity based on a combination of factors.
Ad selection and playback is regulated by Tap through frequency caps -- time restrictions applied to campaigns, advertisers, ads, industries, and sometimes ad creative, which limit the frequency at which those items can occur in proximity to each other. If you hear safeguard when you don't expect to, there's a good chance that a combination of listener targeting and frequency caps is the culprit.
To fully understand this, consider the types of content that can play during an ad break. The list below shows the content types, listed by priority (highest priority at the top):
Paid ad that matches the targeting parameters for the listener.
Unreserved ad (ad played on unreserved inventory; also known as remnant inventory).
Filler (public service announcement or similar unpaid content).
Safeguard (last-resort music or other audio that loops in order to prevent dead air).
Resorting to safeguard usually means there is a problem with inventory management. This is often due to Tap campaigns that are too aggressively targeted. In other words, the campaigns include so many targeting criteria that the pool of listeners who fit the criteria is very small.
This can also affect campaigns that are not aggressively targeted if those campaigns are all of a similar type (from the same advertiser, or similar industries, etc.). So it might appear that you have a lot of available campaigns for your inventory, but if half of them are so narrowly targeted that they won't be selected for a listener, and the widely targeted ones are too similar, frequency caps could limit the number of campaigns that can be selected for a listener. Frequency caps can affect filler in the same way.
That's when it goes to safeguard, even though you seem to have a lot of ad campaigns and filler to choose from. To resolve the problem, loosen up your campaign targeting and frequency caps. See the tips, below.
Tips to Avoid Problems with Targeting and Frequency Capping
Be careful with ad campaign targeting. Don't apply more targeting than you need to achieve your desired result.
Be sure to book a variety of campaigns so there are many for the system to choose from when it is matching campaigns to inventory.
Make sure your filler campaigns are correctly set up. You need a special "filler advertiser" with its frequency cap set to zero and its "industry type" set to "none."
Be sure to create a variety of filler campaigns, with an eye on content separation. Typically, a filler campaign contains several different ads and creative, all on a similar theme (such as a "Station Promo Filler" campaign and a "PSA Filler" campaign). Set a high frequency cap on each filler campaign to ensure that each filler item comes from a different themed campaign (so you don't hear two station promos in a row). More importantly, each ad in the filler campaign should have a high frequency cap (such as 55 minutes) so you don't play the same filler item played back-to-back. But use caution; only use high frequency caps at the campaign level if you have many filler campaigns to choose from. If you have only a few, you will quickly run out of filler, and end up playing safeguard.