When a player has previously passed when it was his turn to make an Opening bid he clearly has less than 13 points. Therefore all subsequent responses he makes are limit bids with a maximum of 12 points, and Opener may pass at any stage of the bidding.

One-level responses by a Passed hand are the same as if he had not passed previously.
But a new suit bid at the 2- level promises 5+ cards in that suit and 11-12 points.

Weak responses by a Passed Hand :

1. Pass - 1♥ - 2♥     = 6-10 pts, 3+card support (single raise)

2. Pass - 1♦ - 1♠     = 6-12 pts, new 4+card suit at the 1-level (ambiguous, with 11-12 bid 2NT next)

3. Pass - 1♦ - 1NT   = 6-10 pts, no 4-card major

4. Pass - 1♥ - 4♥     = 6-10 HCP, 4+card support, plus void or singleton (still applies as normal)

Strong responses by a Passed hand :

1. Pass - 1♥ - 3♥     = 11-12* pts, 3+card support (jump raise)

2. Pass - 1♦ - 2♠     = 11-12* pts, new 5+card suit at the 2-level

3. Pass - 1♥ - 2NT  = 11-12* pts, no 5-card suit       *or 10 pts and 8 losers

The new suit at the 2-level need not be a jump shift (1♦ - 2♠), but can also be a normal new suit response like 1♦ - 2♣.   Strong responses may also include 10 point hands with 8 losers or less.