The Alpha 99 / 91B has 25vdc @ 7ma at the RELAY jack. This is within the specs of the OMR-109 relay in the Icom radios (60v/500ma), although Icom says it is rated for 16v/500ma. The problem is not the voltage rating, but the spec of the relay for operations per minute. With NO electrical load on the contacts, it is rated for 300 operations per minute, or about 10 wpm QSK CW. Faster than this will cause it to fail prematurely. When there is any electrical load on the contacts, the operations per minute rating is LESS than 10 wpm. NOTE: Alpha 99 amplifiers manufactured after 15 DEC 2002 have 12vdc @ 7ma on the RELAY jack.
This web page explains it very well: Icom FAQIC-761: Use RCA jack on back of radio labeled RELAY.
For all, connect the keying cable to the RELAY jack of Alpha amplifier.
