What are surveillance measures in the stock market?

ASM (Additional Surveillance Measures): An umbrella framework for highly volatile stocks with price/volume spikes, alerting investors to risks.
GSM (Graded Surveillance Measures): A stricter, tiered system within ASM for stocks with poor financials (low P/E, book value) and low transparency, requiring extra caution.
Trade-to-Trade (T2T): A restriction where stocks must be delivered to your demat account before selling, preventing intraday squaring off.
Enhanced Margins/Price Bands: Increased margin requirements or reduced daily price movement limits on heavily scrutinized stocks.