In this paper we are concerned with packet broadcast networks in which users communicate with the central station. The key problem is multiple access of a shared broadcast channel. The performance of a family of SRMA (split-channel reservation multiple access) protocols for multiple access proposed by Tobagi and Kleinrock (1976) is studied. We analyse the performance of SRMA-RM (request message) and modified SRMA-RAM (request answer message) protocols in terms of the throughput and the average packet delay. Bounds on the throughput are also established for both protocols.