In a voice system SPA9000, SPA400 & SPA9xx. SPA400 has 4 PSTN lines. Can we configure these 4 PSTN lines on 4 line buttons of SPA942 as a line selector. If line busy: shows red, if line free: shows green similar to the normal PBX system. Also can we assign a speed dial number (mobile phone number) on these line buttons, if yes, how?