I haven't found anything in the manual on this. Does anyone know how/if a call can be sent to VM while ringing? When I see the CID is likely a robocall I want to send it to VM without picking up. I've recorded a SIT as the OGM in hopes the robocaller will recognize it and delete the number. I'm getting calls from "Carmen at cardmember services" several times a day among others. Blocking numbers is useless as they spoof a different CID daily. I've read that sending the SIT may be effective. If I wait till VM normally picks up they will have already hung up and shortening the time wouldn't give a chance me to pick up legit calls.
You can get a SIT file here: https://goo.gl/6tKqgI

No, you'd have to answer then send to voicemail or just let it ring until picked up by auto attendant, not what you want I know. To do what you've described would require hitting a button, why not just hit the line button and immediately hang up, take about the same amount of effort.

Or....

Have some fun. In lieu of hitting the line button, then hanging up...

Hit the line button, then "Hold". Always interesting to see how long they stay on the line...

Answer and hang up is what I do now but the reason I want to send it straight to VM is to send the SIT. The SIT tells the robocall switch that the line is not in service and they theoretically delete it from their calling list. In essence I want the phone to do what a cellphone does with the Reject Call feature. Oh well, back to the drawing board. Maybe I can find a little MP3 player with a speaker to hold up to the phone.

I would think that would be pretty aggravating to anyone who really wanted to leave a message, unless your tone is on an unused voicemail you could send it to. Wouldn't it do the same if you answered and immediately transferred to VM?

I think I have a potential solution. I found a TeleZapper TZ900 for 15 bucks that automatically plays the 3 tone SIT when the phone is answered. Of course that means that legit calls would hear it so, using a momentary DPDT switch, I'm going to build what Bell used to call a "special assembly" (IOW anything that didn't have a USOC) so I can push a button to put the Telezapper in the circuit only when I want to send the tones. If nothing else this should provide an afternoon of "retired guy" entertainment. I'll post back when I have results which will be measured by fewer calls from "Carmen at cardmember services" et al.

Don't knock Carmen.......

Well, I'm back with an update. It's too early to tell if the calls will stop as I've only used it once so far but I did get the thing built. When I'm at my desk and a suspected robocall rings in, I press and hold the button while answering the line. The three tone SIT is then sent. Before, when I answered the line I would say nothing and within a few seconds I would hear the "Hello, this is Carmen from cardmember services..." message. When I answered with the SIT there was few seconds of silence and then the call disconnected. Assuming this was the same daily robocall from "Carmen," which I suspect it was based on the number, it seems to have worked.
The TeleZapper has an RJ11 at each end and can be placed between the phone and the CO line or plugged into the CO line without a phone. It's normally triggered whenever a ringing line is answered. So the push button I added is used to just momentarily connect the device to the line while answering sparing the ears of legit callers. I used a 2 port surface mount jack to house the push button switch which is wired between the two jacks. The TZ plugs into one and the line into the other.
I bought the TeleZapper on Amazon at half price as a "Used: LikeNew" item and when it arrived it didn't work. I replaced the coin battery inside to resolve that and it's good to go.

Thanks for the update, let us know if it truly works.